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	$166.39	8.658%	$180.796	$180.80	$180.80	$180.80
Purchase #2	$138.35	10.764%	$153.242	$153.24	$153.25	$153.20
Purchase #3	$147.46	8.734%	$160.3392	$160.34	$160.35	$160.30
Purchase #4	$165.34	9.644%	$181.2854	$181.29	$181.30	$181.30
Purchase #5	$247.66	12.612%	$278.8949	$278.89	$278.90	$278.90
Purchase #6	$181.54	12.859%	$204.8842	$204.88	$204.90	$204.90
Purchase #7	$91.73	12.501%	$103.1972	$103.20	$103.20	$103.20
7 purchase totals =	$1,138.47		$1,262.6389	$1,262.64	$1,262.70	$1,262.60