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	$35.57	6.625%	$37.9265	$37.93	$37.95	$37.90
Purchase #2	$94.79	3.107%	$97.7351	$97.74	$97.75	$97.70
Purchase #3	$232.72	4.525%	$243.2506	$243.25	$243.25	$243.30
Purchase #4	$207.39	9.728%	$227.5649	$227.56	$227.55	$227.60
Purchase #5	$73.41	10.550%	$81.1548	$81.15	$81.15	$81.20
Purchase #6	$214.83	8.683%	$233.4837	$233.48	$233.50	$233.50
Purchase #7	$161.83	12.667%	$182.329	$182.33	$182.35	$182.30
7 purchase totals =	$1,020.54		$1,103.4446	$1,103.44	$1,103.50	$1,103.50