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	$143.71	5.573%	$151.719	$151.72	$151.70	$151.70
Purchase #2	$137.73	11.765%	$153.9339	$153.93	$153.95	$153.90
Purchase #3	$30.35	10.506%	$33.5386	$33.54	$33.55	$33.50
Purchase #4	$153.27	8.398%	$166.1416	$166.14	$166.15	$166.10
Purchase #5	$212.94	13.265%	$241.1865	$241.19	$241.20	$241.20
Purchase #6	$145.67	3.543%	$150.8311	$150.83	$150.85	$150.80
Purchase #7	$186.34	13.223%	$210.9797	$210.98	$211.00	$211.00
7 purchase totals =	$1,010.01		$1,108.3304	$1,108.33	$1,108.40	$1,108.20