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	$190.65	5.173%	$200.5123	$200.51	$200.50	$200.50
Purchase #2	$85.80	3.194%	$88.5405	$88.54	$88.55	$88.50
Purchase #3	$14.58	8.184%	$15.7732	$15.77	$15.75	$15.80
Purchase #4	$68.58	4.310%	$71.5358	$71.54	$71.55	$71.50
Purchase #5	$88.47	10.531%	$97.7868	$97.79	$97.80	$97.80
Purchase #6	$245.79	5.131%	$258.4015	$258.40	$258.40	$258.40
Purchase #7	$150.76	9.109%	$164.4927	$164.49	$164.50	$164.50
7 purchase totals =	$844.63		$897.0428	$897.04	$897.05	$897.00