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	$75.39	11.549%	$84.0968	$84.10	$84.10	$84.10
Purchase #2	$73.93	6.314%	$78.5979	$78.60	$78.60	$78.60
Purchase #3	$214.47	3.809%	$222.6392	$222.64	$222.65	$222.60
Purchase #4	$229.47	10.584%	$253.7571	$253.76	$253.75	$253.80
Purchase #5	$66.98	5.847%	$70.8963	$70.90	$70.90	$70.90
Purchase #6	$149.73	13.468%	$169.8956	$169.90	$169.90	$169.90
Purchase #7	$226.91	9.704%	$248.9293	$248.93	$248.95	$248.90
7 purchase totals =	$1,036.88		$1,128.8122	$1,128.83	$1,128.85	$1,128.80