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	$77.50	10.149%	$85.3655	$85.37	$85.35	$85.40
Purchase #2	$167.35	10.114%	$184.2758	$184.28	$184.30	$184.30
Purchase #3	$10.65	8.562%	$11.5619	$11.56	$11.55	$11.60
Purchase #4	$64.27	7.662%	$69.1944	$69.19	$69.20	$69.20
Purchase #5	$158.32	6.555%	$168.6979	$168.70	$168.70	$168.70
Purchase #6	$156.88	10.223%	$172.9178	$172.92	$172.90	$172.90
Purchase #7	$199.91	9.263%	$218.4277	$218.43	$218.45	$218.40
7 purchase totals =	$834.88		$910.4410	$910.45	$910.45	$910.50