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	$55.67	6.535%	$59.308	$59.31	$59.30	$59.30
Purchase #2	$173.93	13.826%	$197.9776	$197.98	$198.00	$198.00
Purchase #3	$67.28	12.356%	$75.5931	$75.59	$75.60	$75.60
Purchase #4	$209.55	6.565%	$223.307	$223.31	$223.30	$223.30
Purchase #5	$175.89	8.583%	$190.9866	$190.99	$191.00	$191.00
Purchase #6	$205.25	11.384%	$228.6157	$228.62	$228.60	$228.60
Purchase #7	$57.98	5.474%	$61.1538	$61.15	$61.15	$61.20
7 purchase totals =	$945.55		$1,036.9418	$1,036.95	$1,036.95	$1,037.00