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	$226.41	12.416%	$254.5211	$254.52	$254.50	$254.50
Purchase #2	$206.81	12.451%	$232.5599	$232.56	$232.55	$232.60
Purchase #3	$65.33	13.107%	$73.8928	$73.89	$73.90	$73.90
Purchase #4	$79.52	7.844%	$85.7575	$85.76	$85.75	$85.80
Purchase #5	$137.57	11.375%	$153.2186	$153.22	$153.20	$153.20
Purchase #6	$223.82	8.106%	$241.9628	$241.96	$241.95	$242.00
Purchase #7	$57.62	3.184%	$59.4546	$59.45	$59.45	$59.50
7 purchase totals =	$997.08		$1,101.3673	$1,101.36	$1,101.30	$1,101.50