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	$183.98	5.312%	$193.753	$193.75	$193.75	$193.80
Purchase #2	$148.79	6.697%	$158.7545	$158.75	$158.75	$158.80
Purchase #3	$83.63	8.389%	$90.6457	$90.65	$90.65	$90.60
Purchase #4	$180.58	5.493%	$190.4993	$190.50	$190.50	$190.50
Purchase #5	$39.92	6.171%	$42.3835	$42.38	$42.40	$42.40
Purchase #6	$181.33	13.798%	$206.3499	$206.35	$206.35	$206.30
Purchase #7	$99.32	4.256%	$103.5471	$103.55	$103.55	$103.50
7 purchase totals =	$917.55		$985.9330	$985.93	$985.95	$985.90