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	$34.90	8.113%	$37.7314	$37.73	$37.75	$37.70
Purchase #2	$19.62	7.518%	$21.095	$21.10	$21.10	$21.10
Purchase #3	$50.66	6.183%	$53.7923	$53.79	$53.80	$53.80
Purchase #4	$238.28	11.183%	$264.9269	$264.93	$264.95	$264.90
Purchase #5	$148.68	11.764%	$166.1707	$166.17	$166.15	$166.20
Purchase #6	$86.46	13.192%	$97.8658	$97.87	$97.85	$97.90
Purchase #7	$84.70	7.288%	$90.8729	$90.87	$90.85	$90.90
7 purchase totals =	$663.30		$732.4550	$732.46	$732.45	$732.50