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	$164.68	9.409%	$180.1747	$180.17	$180.15	$180.20
Purchase #2	$135.83	8.580%	$147.4842	$147.48	$147.50	$147.50
Purchase #3	$209.29	9.528%	$229.2312	$229.23	$229.25	$229.20
Purchase #4	$65.25	9.327%	$71.3359	$71.34	$71.35	$71.30
Purchase #5	$115.93	10.288%	$127.8569	$127.86	$127.85	$127.90
Purchase #6	$144.95	11.766%	$162.0048	$162.00	$162.00	$162.00
Purchase #7	$167.67	11.773%	$187.4098	$187.41	$187.40	$187.40
7 purchase totals =	$1,003.60		$1,105.4975	$1,105.49	$1,105.50	$1,105.50