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	$56.66	12.324%	$63.6428	$63.64	$63.65	$63.60
Purchase #2	$236.59	5.633%	$249.9171	$249.92	$249.90	$249.90
Purchase #3	$123.58	11.572%	$137.8807	$137.88	$137.90	$137.90
Purchase #4	$185.97	5.420%	$196.0496	$196.05	$196.05	$196.00
Purchase #5	$234.29	10.297%	$258.4148	$258.41	$258.40	$258.40
Purchase #6	$155.50	10.158%	$171.2957	$171.30	$171.30	$171.30
Purchase #7	$179.34	6.815%	$191.562	$191.56	$191.55	$191.60
7 purchase totals =	$1,171.93		$1,268.7627	$1,268.76	$1,268.75	$1,268.70