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	$173.33	10.164%	$190.9473	$190.95	$190.95	$190.90
Purchase #2	$170.61	13.777%	$194.1149	$194.11	$194.10	$194.10
Purchase #3	$165.86	13.684%	$188.5563	$188.56	$188.55	$188.60
Purchase #4	$53.84	7.442%	$57.8468	$57.85	$57.85	$57.80
Purchase #5	$168.70	13.300%	$191.1371	$191.14	$191.15	$191.10
Purchase #6	$151.84	6.730%	$162.0588	$162.06	$162.05	$162.10
Purchase #7	$185.73	9.762%	$203.861	$203.86	$203.85	$203.90
7 purchase totals =	$1,069.91		$1,188.5222	$1,188.53	$1,188.50	$1,188.50