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	$90.68	8.191%	$98.1076	$98.11	$98.10	$98.10
Purchase #2	$228.71	7.786%	$246.5174	$246.52	$246.50	$246.50
Purchase #3	$35.87	5.272%	$37.7611	$37.76	$37.75	$37.80
Purchase #4	$74.29	10.248%	$81.9032	$81.90	$81.90	$81.90
Purchase #5	$168.47	7.132%	$180.4853	$180.49	$180.50	$180.50
Purchase #6	$250.25	6.352%	$266.1459	$266.15	$266.15	$266.10
Purchase #7	$191.59	13.560%	$217.5696	$217.57	$217.55	$217.60
7 purchase totals =	$1,039.86		$1,128.4901	$1,128.50	$1,128.45	$1,128.50