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	$86.75	11.315%	$96.5658	$96.57	$96.55	$96.60
Purchase #2	$243.83	4.651%	$255.1705	$255.17	$255.15	$255.20
Purchase #3	$145.41	7.812%	$156.7694	$156.77	$156.75	$156.80
Purchase #4	$61.85	10.810%	$68.536	$68.54	$68.55	$68.50
Purchase #5	$52.40	5.707%	$55.3905	$55.39	$55.40	$55.40
Purchase #6	$100.29	3.152%	$103.4511	$103.45	$103.45	$103.50
Purchase #7	$58.66	3.714%	$60.8386	$60.84	$60.85	$60.80
7 purchase totals =	$749.19		$796.7219	$796.73	$796.70	$796.80