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	$56.59	11.773%	$63.2523	$63.25	$63.25	$63.30
Purchase #2	$84.78	6.378%	$90.1873	$90.19	$90.20	$90.20
Purchase #3	$64.27	4.583%	$67.2155	$67.22	$67.20	$67.20
Purchase #4	$71.29	12.575%	$80.2547	$80.25	$80.25	$80.30
Purchase #5	$104.88	6.567%	$111.7675	$111.77	$111.75	$111.80
Purchase #6	$172.35	13.179%	$195.064	$195.06	$195.05	$195.10
Purchase #7	$160.54	13.155%	$181.659	$181.66	$181.65	$181.70
7 purchase totals =	$714.70		$789.4003	$789.40	$789.35	$789.60