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	$90.89	11.375%	$101.2287	$101.23	$101.25	$101.20
Purchase #2	$72.33	11.305%	$80.5069	$80.51	$80.50	$80.50
Purchase #3	$125.47	12.183%	$140.756	$140.76	$140.75	$140.80
Purchase #4	$90.94	9.731%	$99.7894	$99.79	$99.80	$99.80
Purchase #5	$105.30	10.772%	$116.6429	$116.64	$116.65	$116.60
Purchase #6	$118.85	7.739%	$128.0478	$128.05	$128.05	$128.00
Purchase #7	$32.57	9.720%	$35.7358	$35.74	$35.75	$35.70
7 purchase totals =	$636.35		$702.7075	$702.72	$702.75	$702.60