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	$117.71	5.150%	$123.7721	$123.77	$123.75	$123.80
Purchase #2	$161.53	5.181%	$169.8989	$169.90	$169.90	$169.90
Purchase #3	$249.33	10.751%	$276.1355	$276.14	$276.15	$276.10
Purchase #4	$206.95	7.421%	$222.3078	$222.31	$222.30	$222.30
Purchase #5	$199.32	12.364%	$223.9639	$223.96	$223.95	$224.00
Purchase #6	$56.84	8.606%	$61.7317	$61.73	$61.75	$61.70
Purchase #7	$234.57	4.672%	$245.5291	$245.53	$245.55	$245.50
7 purchase totals =	$1,226.25		$1,323.3390	$1,323.34	$1,323.35	$1,323.30