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	$177.84	7.225%	$190.6889	$190.69	$190.70	$190.70
Purchase #2	$69.64	3.849%	$72.3204	$72.32	$72.30	$72.30
Purchase #3	$201.58	4.456%	$210.5624	$210.56	$210.55	$210.60
Purchase #4	$190.78	12.253%	$214.1563	$214.16	$214.15	$214.20
Purchase #5	$204.54	3.134%	$210.9503	$210.95	$210.95	$211.00
Purchase #6	$34.32	11.637%	$38.3138	$38.31	$38.30	$38.30
Purchase #7	$93.35	12.795%	$105.2941	$105.29	$105.30	$105.30
7 purchase totals =	$972.05		$1,042.2862	$1,042.28	$1,042.25	$1,042.40