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	$73.74	5.113%	$77.5103	$77.51	$77.50	$77.50
Purchase #2	$202.88	12.102%	$227.4325	$227.43	$227.45	$227.40
Purchase #3	$99.79	13.839%	$113.5999	$113.60	$113.60	$113.60
Purchase #4	$225.43	4.291%	$235.1032	$235.10	$235.10	$235.10
Purchase #5	$83.59	11.229%	$92.9763	$92.98	$93.00	$93.00
Purchase #6	$237.89	13.153%	$269.1797	$269.18	$269.20	$269.20
Purchase #7	$118.90	10.358%	$131.2157	$131.22	$131.20	$131.20
7 purchase totals =	$1,042.22		$1,147.0176	$1,147.02	$1,147.05	$1,147.00