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	$147.68	11.577%	$164.7769	$164.78	$164.80	$164.80
Purchase #2	$223.33	4.792%	$234.032	$234.03	$234.05	$234.00
Purchase #3	$120.54	13.485%	$136.7948	$136.79	$136.80	$136.80
Purchase #4	$173.97	8.155%	$188.1573	$188.16	$188.15	$188.20
Purchase #5	$156.71	12.836%	$176.8253	$176.83	$176.85	$176.80
Purchase #6	$173.90	8.324%	$188.3754	$188.38	$188.40	$188.40
Purchase #7	$6.73	11.742%	$7.5202	$7.52	$7.50	$7.50
7 purchase totals =	$1,002.86		$1,096.4819	$1,096.49	$1,096.55	$1,096.50