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	$203.65	3.360%	$210.4926	$210.49	$210.50	$210.50
Purchase #2	$241.92	3.394%	$250.1308	$250.13	$250.15	$250.10
Purchase #3	$5.62	12.218%	$6.3067	$6.31	$6.30	$6.30
Purchase #4	$128.29	10.306%	$141.5116	$141.51	$141.50	$141.50
Purchase #5	$118.64	13.231%	$134.3373	$134.34	$134.35	$134.30
Purchase #6	$241.95	13.568%	$274.7778	$274.78	$274.80	$274.80
Purchase #7	$139.57	3.785%	$144.8527	$144.85	$144.85	$144.90
7 purchase totals =	$1,079.64		$1,162.4095	$1,162.41	$1,162.45	$1,162.40