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	$168.47	7.148%	$180.5122	$180.51	$180.50	$180.50
Purchase #2	$72.59	3.294%	$74.9811	$74.98	$75.00	$75.00
Purchase #3	$140.75	11.342%	$156.7139	$156.71	$156.70	$156.70
Purchase #4	$64.74	11.223%	$72.0058	$72.01	$72.00	$72.00
Purchase #5	$154.29	4.496%	$161.2269	$161.23	$161.25	$161.20
Purchase #6	$197.28	6.188%	$209.4877	$209.49	$209.50	$209.50
Purchase #7	$111.67	10.379%	$123.2602	$123.26	$123.25	$123.30
7 purchase totals =	$909.79		$978.1878	$978.19	$978.20	$978.20