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	$153.51	10.308%	$169.3338	$169.33	$169.35	$169.30
Purchase #2	$183.38	7.131%	$196.4568	$196.46	$196.45	$196.50
Purchase #3	$96.64	4.584%	$101.07	$101.07	$101.05	$101.10
Purchase #4	$142.46	3.164%	$146.9674	$146.97	$146.95	$147.00
Purchase #5	$216.26	10.432%	$238.8202	$238.82	$238.80	$238.80
Purchase #6	$185.61	12.498%	$208.8075	$208.81	$208.80	$208.80
Purchase #7	$171.60	11.460%	$191.2654	$191.27	$191.25	$191.30
7 purchase totals =	$1,149.46		$1,252.7211	$1,252.73	$1,252.65	$1,252.80