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	$241.27	9.102%	$263.2304	$263.23	$263.25	$263.20
Purchase #2	$175.33	9.325%	$191.6795	$191.68	$191.70	$191.70
Purchase #3	$72.26	6.704%	$77.1043	$77.10	$77.10	$77.10
Purchase #4	$223.85	4.653%	$234.2657	$234.27	$234.25	$234.30
Purchase #5	$152.97	7.445%	$164.3586	$164.36	$164.35	$164.40
Purchase #6	$151.98	10.227%	$167.523	$167.52	$167.50	$167.50
Purchase #7	$17.76	4.530%	$18.5645	$18.56	$18.55	$18.60
7 purchase totals =	$1,035.42		$1,116.7260	$1,116.72	$1,116.70	$1,116.80