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	$142.52	6.824%	$152.2456	$152.25	$152.25	$152.20
Purchase #2	$41.56	11.256%	$46.238	$46.24	$46.25	$46.20
Purchase #3	$150.57	9.626%	$165.0639	$165.06	$165.05	$165.10
Purchase #4	$114.56	8.698%	$124.5244	$124.52	$124.50	$124.50
Purchase #5	$88.65	4.579%	$92.7093	$92.71	$92.70	$92.70
Purchase #6	$64.33	5.128%	$67.6288	$67.63	$67.65	$67.60
Purchase #7	$194.47	10.725%	$215.3269	$215.33	$215.35	$215.30
7 purchase totals =	$796.66		$863.7369	$863.74	$863.75	$863.60