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	$88.38	3.290%	$91.2877	$91.29	$91.30	$91.30
Purchase #2	$228.87	10.808%	$253.6063	$253.61	$253.60	$253.60
Purchase #3	$22.33	5.303%	$23.5142	$23.51	$23.50	$23.50
Purchase #4	$119.41	8.511%	$129.573	$129.57	$129.55	$129.60
Purchase #5	$147.32	12.312%	$165.458	$165.46	$165.45	$165.50
Purchase #6	$250.61	7.528%	$269.4759	$269.48	$269.50	$269.50
Purchase #7	$131.49	7.679%	$141.5871	$141.59	$141.60	$141.60
7 purchase totals =	$988.41		$1,074.5022	$1,074.51	$1,074.50	$1,074.60