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	$80.89	5.762%	$85.5509	$85.55	$85.55	$85.60
Purchase #2	$226.76	13.139%	$256.554	$256.55	$256.55	$256.60
Purchase #3	$167.42	8.641%	$181.8868	$181.89	$181.90	$181.90
Purchase #4	$223.30	6.716%	$238.2968	$238.30	$238.30	$238.30
Purchase #5	$114.85	8.327%	$124.4136	$124.41	$124.40	$124.40
Purchase #6	$231.73	6.802%	$247.4923	$247.49	$247.50	$247.50
Purchase #7	$38.96	5.601%	$41.1421	$41.14	$41.15	$41.10
7 purchase totals =	$1,083.91		$1,175.3365	$1,175.33	$1,175.35	$1,175.40