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	$69.82	3.641%	$72.3621	$72.36	$72.35	$72.40
Purchase #2	$59.95	11.517%	$66.8544	$66.85	$66.85	$66.90
Purchase #3	$206.56	13.489%	$234.4229	$234.42	$234.40	$234.40
Purchase #4	$110.76	12.512%	$124.6183	$124.62	$124.60	$124.60
Purchase #5	$193.67	10.188%	$213.4011	$213.40	$213.40	$213.40
Purchase #6	$174.35	6.193%	$185.1475	$185.15	$185.15	$185.10
Purchase #7	$192.89	5.623%	$203.7362	$203.74	$203.75	$203.70
7 purchase totals =	$1,008.00		$1,100.5425	$1,100.54	$1,100.50	$1,100.50