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	$71.54	7.690%	$77.0414	$77.04	$77.05	$77.00
Purchase #2	$114.59	9.600%	$125.5906	$125.59	$125.60	$125.60
Purchase #3	$37.88	12.355%	$42.5601	$42.56	$42.55	$42.60
Purchase #4	$98.89	3.274%	$102.1277	$102.13	$102.15	$102.10
Purchase #5	$196.45	4.870%	$206.0171	$206.02	$206.00	$206.00
Purchase #6	$111.84	8.329%	$121.1552	$121.16	$121.15	$121.20
Purchase #7	$54.61	9.450%	$59.7706	$59.77	$59.75	$59.80
7 purchase totals =	$685.80		$734.2627	$734.27	$734.25	$734.30