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	$96.29	4.341%	$100.4699	$100.47	$100.45	$100.50
Purchase #2	$194.90	8.737%	$211.9284	$211.93	$211.95	$211.90
Purchase #3	$52.37	11.651%	$58.4716	$58.47	$58.45	$58.50
Purchase #4	$95.47	5.230%	$100.4631	$100.46	$100.45	$100.50
Purchase #5	$55.29	3.120%	$57.015	$57.02	$57.00	$57.00
Purchase #6	$129.44	9.231%	$141.3886	$141.39	$141.40	$141.40
Purchase #7	$185.87	11.203%	$206.693	$206.69	$206.70	$206.70
7 purchase totals =	$809.63		$876.4296	$876.43	$876.40	$876.50