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	$48.33	6.212%	$51.3323	$51.33	$51.35	$51.30
Purchase #2	$245.76	10.396%	$271.3092	$271.31	$271.30	$271.30
Purchase #3	$209.39	11.442%	$233.3484	$233.35	$233.35	$233.30
Purchase #4	$236.64	10.815%	$262.2326	$262.23	$262.25	$262.20
Purchase #5	$220.76	5.792%	$233.5464	$233.55	$233.55	$233.50
Purchase #6	$51.89	13.609%	$58.9517	$58.95	$58.95	$59.00
Purchase #7	$171.75	3.412%	$177.6101	$177.61	$177.60	$177.60
7 purchase totals =	$1,184.52		$1,288.3307	$1,288.33	$1,288.35	$1,288.20