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	$162.82	7.811%	$175.5379	$175.54	$175.55	$175.50
Purchase #2	$247.76	6.372%	$263.5473	$263.55	$263.55	$263.50
Purchase #3	$172.98	9.135%	$188.7817	$188.78	$188.80	$188.80
Purchase #4	$15.49	12.314%	$17.3974	$17.40	$17.40	$17.40
Purchase #5	$136.66	7.284%	$146.6143	$146.61	$146.60	$146.60
Purchase #6	$131.50	7.614%	$141.5124	$141.51	$141.50	$141.50
Purchase #7	$141.26	7.428%	$151.7528	$151.75	$151.75	$151.80
7 purchase totals =	$1,008.47		$1,085.1438	$1,085.14	$1,085.15	$1,085.10