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	$211.47	8.366%	$229.1616	$229.16	$229.15	$229.20
Purchase #2	$35.68	4.132%	$37.1543	$37.15	$37.15	$37.20
Purchase #3	$52.41	13.748%	$59.6153	$59.62	$59.60	$59.60
Purchase #4	$231.82	5.372%	$244.2734	$244.27	$244.25	$244.30
Purchase #5	$175.33	8.869%	$190.88	$190.88	$190.90	$190.90
Purchase #6	$232.52	12.268%	$261.0456	$261.05	$261.05	$261.00
Purchase #7	$219.63	13.543%	$249.3745	$249.37	$249.35	$249.40
7 purchase totals =	$1,158.86		$1,271.5047	$1,271.50	$1,271.45	$1,271.60