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	$169.97	3.225%	$175.4515	$175.45	$175.45	$175.50
Purchase #2	$249.74	6.178%	$265.1689	$265.17	$265.15	$265.20
Purchase #3	$130.31	4.631%	$136.3447	$136.34	$136.35	$136.30
Purchase #4	$244.68	7.219%	$262.3434	$262.34	$262.35	$262.30
Purchase #5	$86.66	11.162%	$96.333	$96.33	$96.35	$96.30
Purchase #6	$190.56	9.234%	$208.1563	$208.16	$208.15	$208.20
Purchase #7	$80.54	12.742%	$90.8024	$90.80	$90.80	$90.80
7 purchase totals =	$1,152.46		$1,234.6002	$1,234.59	$1,234.60	$1,234.60