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	$153.65	7.564%	$165.2721	$165.27	$165.25	$165.30
Purchase #2	$58.88	12.632%	$66.3177	$66.32	$66.30	$66.30
Purchase #3	$38.33	6.310%	$40.7486	$40.75	$40.75	$40.70
Purchase #4	$56.94	13.778%	$64.7852	$64.79	$64.80	$64.80
Purchase #5	$148.67	12.593%	$167.392	$167.39	$167.40	$167.40
Purchase #6	$88.42	8.799%	$96.2001	$96.20	$96.20	$96.20
Purchase #7	$170.51	10.395%	$188.2345	$188.23	$188.25	$188.20
7 purchase totals =	$715.40		$788.9502	$788.95	$788.95	$788.90