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	$164.28	4.838%	$172.2279	$172.23	$172.25	$172.20
Purchase #2	$128.74	10.134%	$141.7865	$141.79	$141.80	$141.80
Purchase #3	$18.83	11.224%	$20.9435	$20.94	$20.95	$20.90
Purchase #4	$185.90	5.268%	$195.6932	$195.69	$195.70	$195.70
Purchase #5	$198.36	12.666%	$223.4843	$223.48	$223.50	$223.50
Purchase #6	$78.71	5.796%	$83.272	$83.27	$83.25	$83.30
Purchase #7	$96.68	8.259%	$104.6648	$104.66	$104.65	$104.70
7 purchase totals =	$871.50		$942.0722	$942.06	$942.10	$942.10