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	$185.34	3.408%	$191.6564	$191.66	$191.65	$191.70
Purchase #2	$168.34	3.464%	$174.1713	$174.17	$174.15	$174.20
Purchase #3	$53.82	12.620%	$60.6121	$60.61	$60.60	$60.60
Purchase #4	$111.42	13.835%	$126.835	$126.84	$126.85	$126.80
Purchase #5	$143.62	11.340%	$159.9065	$159.91	$159.90	$159.90
Purchase #6	$174.56	6.258%	$185.484	$185.48	$185.50	$185.50
Purchase #7	$171.97	8.781%	$187.0707	$187.07	$187.05	$187.10
7 purchase totals =	$1,009.07		$1,085.7360	$1,085.74	$1,085.70	$1,085.80