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	$173.90	7.210%	$186.4382	$186.44	$186.45	$186.40
Purchase #2	$152.90	12.161%	$171.4942	$171.49	$171.50	$171.50
Purchase #3	$140.89	5.860%	$149.1462	$149.15	$149.15	$149.10
Purchase #4	$7.61	11.109%	$8.4554	$8.46	$8.45	$8.50
Purchase #5	$214.83	13.162%	$243.1059	$243.11	$243.10	$243.10
Purchase #6	$233.78	3.671%	$242.3621	$242.36	$242.35	$242.40
Purchase #7	$95.56	4.660%	$100.0131	$100.01	$100.00	$100.00
7 purchase totals =	$1,019.47		$1,101.0151	$1,101.02	$1,101.00	$1,101.00