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	$110.59	11.692%	$123.5202	$123.52	$123.50	$123.50
Purchase #2	$155.94	8.375%	$169	$169.00	$169.00	$169.00
Purchase #3	$189.33	3.447%	$195.8562	$195.86	$195.85	$195.90
Purchase #4	$109.80	4.301%	$114.5225	$114.52	$114.50	$114.50
Purchase #5	$233.51	11.516%	$260.401	$260.40	$260.40	$260.40
Purchase #6	$229.47	13.323%	$260.0423	$260.04	$260.05	$260.00
Purchase #7	$45.27	6.525%	$48.2239	$48.22	$48.20	$48.20
7 purchase totals =	$1,073.91		$1,171.5661	$1,171.56	$1,171.50	$1,171.50