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	$216.64	10.435%	$239.2464	$239.25	$239.25	$239.20
Purchase #2	$27.25	3.766%	$28.2762	$28.28	$28.30	$28.30
Purchase #3	$196.87	11.500%	$219.5101	$219.51	$219.50	$219.50
Purchase #4	$64.53	10.109%	$71.0533	$71.05	$71.05	$71.10
Purchase #5	$72.65	13.330%	$82.3342	$82.33	$82.35	$82.30
Purchase #6	$146.29	8.131%	$158.1848	$158.18	$158.20	$158.20
Purchase #7	$109.82	4.509%	$114.7718	$114.77	$114.75	$114.80
7 purchase totals =	$834.05		$913.3768	$913.37	$913.40	$913.40