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	$178.54	6.485%	$190.1183	$190.12	$190.10	$190.10
Purchase #2	$211.72	5.211%	$222.7527	$222.75	$222.75	$222.80
Purchase #3	$250.46	4.390%	$261.4552	$261.46	$261.45	$261.50
Purchase #4	$210.59	6.725%	$224.7522	$224.75	$224.75	$224.80
Purchase #5	$68.66	5.740%	$72.6011	$72.60	$72.60	$72.60
Purchase #6	$66.76	4.178%	$69.5492	$69.55	$69.55	$69.50
Purchase #7	$128.85	10.154%	$141.9334	$141.93	$141.95	$141.90
7 purchase totals =	$1,115.58		$1,183.1621	$1,183.16	$1,183.15	$1,183.20