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	$40.53	11.184%	$45.0629	$45.06	$45.05	$45.10
Purchase #2	$235.86	3.194%	$243.3934	$243.39	$243.40	$243.40
Purchase #3	$142.88	11.853%	$159.8156	$159.82	$159.80	$159.80
Purchase #4	$212.50	6.546%	$226.4103	$226.41	$226.40	$226.40
Purchase #5	$38.53	9.763%	$42.2917	$42.29	$42.30	$42.30
Purchase #6	$232.26	10.458%	$256.5498	$256.55	$256.55	$256.50
Purchase #7	$170.90	5.862%	$180.9182	$180.92	$180.90	$180.90
7 purchase totals =	$1,073.46		$1,154.4419	$1,154.44	$1,154.40	$1,154.40