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	$227.32	11.660%	$253.8255	$253.83	$253.85	$253.80
Purchase #2	$92.74	7.438%	$99.638	$99.64	$99.65	$99.60
Purchase #3	$229.54	5.801%	$242.8556	$242.86	$242.85	$242.90
Purchase #4	$139.44	3.103%	$143.7668	$143.77	$143.75	$143.80
Purchase #5	$182.97	4.316%	$190.867	$190.87	$190.85	$190.90
Purchase #6	$201.32	10.193%	$221.8405	$221.84	$221.85	$221.80
Purchase #7	$17.62	5.129%	$18.5237	$18.52	$18.50	$18.50
7 purchase totals =	$1,090.95		$1,171.3171	$1,171.33	$1,171.30	$1,171.30