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	$93.37	6.289%	$99.242	$99.24	$99.25	$99.20
Purchase #2	$193.60	3.763%	$200.8852	$200.89	$200.90	$200.90
Purchase #3	$117.62	11.826%	$131.5297	$131.53	$131.55	$131.50
Purchase #4	$144.41	13.146%	$163.3941	$163.39	$163.40	$163.40
Purchase #5	$50.43	12.241%	$56.6031	$56.60	$56.60	$56.60
Purchase #6	$102.89	3.219%	$106.202	$106.20	$106.20	$106.20
Purchase #7	$121.33	5.265%	$127.718	$127.72	$127.70	$127.70
7 purchase totals =	$823.65		$885.5741	$885.57	$885.60	$885.50