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	$201.45	4.408%	$210.3299	$210.33	$210.35	$210.30
Purchase #2	$215.43	7.164%	$230.8634	$230.86	$230.85	$230.90
Purchase #3	$174.85	8.204%	$189.1947	$189.19	$189.20	$189.20
Purchase #4	$174.29	8.149%	$188.4929	$188.49	$188.50	$188.50
Purchase #5	$127.94	4.692%	$133.9429	$133.94	$133.95	$133.90
Purchase #6	$81.92	11.610%	$91.4309	$91.43	$91.45	$91.40
Purchase #7	$37.87	12.655%	$42.6624	$42.66	$42.65	$42.70
7 purchase totals =	$1,013.75		$1,086.9171	$1,086.90	$1,086.95	$1,086.90