Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.48	13.560%	$127.7323	$127.73	$127.75	$127.70
Purchase #2	$208.37	4.640%	$218.0384	$218.04	$218.05	$218.00
Purchase #3	$249.52	5.869%	$264.1643	$264.16	$264.15	$264.20
Purchase #4	$191.89	12.682%	$216.2255	$216.23	$216.25	$216.20
Purchase #5	$197.54	10.447%	$218.177	$218.18	$218.20	$218.20
Purchase #6	$162.99	10.829%	$180.6402	$180.64	$180.65	$180.60
Purchase #7	$99.42	13.228%	$112.5713	$112.57	$112.55	$112.60
7 purchase totals =	$1,222.21		$1,337.5490	$1,337.55	$1,337.60	$1,337.50