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	$52.27	13.140%	$59.1383	$59.14	$59.15	$59.10
Purchase #2	$216.98	11.748%	$242.4708	$242.47	$242.45	$242.50
Purchase #3	$175.37	5.186%	$184.4647	$184.46	$184.45	$184.50
Purchase #4	$28.84	3.624%	$29.8852	$29.89	$29.90	$29.90
Purchase #5	$222.89	9.120%	$243.2176	$243.22	$243.20	$243.20
Purchase #6	$250.67	5.448%	$264.3265	$264.33	$264.35	$264.30
Purchase #7	$152.99	6.785%	$163.3704	$163.37	$163.35	$163.40
7 purchase totals =	$1,100.01		$1,186.8735	$1,186.88	$1,186.85	$1,186.90