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	$174.94	12.140%	$196.1777	$196.18	$196.20	$196.20
Purchase #2	$192.47	13.688%	$218.8153	$218.82	$218.80	$218.80
Purchase #3	$130.76	7.577%	$140.6677	$140.67	$140.65	$140.70
Purchase #4	$31.57	3.123%	$32.5559	$32.56	$32.55	$32.60
Purchase #5	$220.51	9.743%	$241.9943	$241.99	$242.00	$242.00
Purchase #6	$91.44	5.736%	$96.685	$96.69	$96.70	$96.70
Purchase #7	$54.99	13.674%	$62.5093	$62.51	$62.50	$62.50
7 purchase totals =	$896.68		$989.4052	$989.42	$989.40	$989.50