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	$218.79	3.667%	$226.813	$226.81	$226.80	$226.80
Purchase #2	$98.61	13.253%	$111.6788	$111.68	$111.70	$111.70
Purchase #3	$140.37	8.802%	$152.7254	$152.73	$152.75	$152.70
Purchase #4	$46.52	8.597%	$50.5193	$50.52	$50.50	$50.50
Purchase #5	$27.59	4.526%	$28.8387	$28.84	$28.85	$28.80
Purchase #6	$5.70	9.310%	$6.2307	$6.23	$6.25	$6.20
Purchase #7	$216.53	10.138%	$238.4818	$238.48	$238.50	$238.50
7 purchase totals =	$754.11		$815.2877	$815.29	$815.35	$815.20