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	$57.83	4.738%	$60.57	$60.57	$60.55	$60.60
Purchase #2	$192.28	12.271%	$215.8747	$215.87	$215.85	$215.90
Purchase #3	$233.50	6.385%	$248.409	$248.41	$248.40	$248.40
Purchase #4	$182.61	12.838%	$206.0535	$206.05	$206.05	$206.10
Purchase #5	$127.57	9.499%	$139.6879	$139.69	$139.70	$139.70
Purchase #6	$82.51	9.251%	$90.143	$90.14	$90.15	$90.10
Purchase #7	$36.94	10.776%	$40.9207	$40.92	$40.90	$40.90
7 purchase totals =	$913.24		$1,001.6588	$1,001.65	$1,001.60	$1,001.70