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	$119.43	7.751%	$128.687	$128.69	$128.70	$128.70
Purchase #2	$122.31	3.103%	$126.1053	$126.11	$126.10	$126.10
Purchase #3	$150.51	11.121%	$167.2482	$167.25	$167.25	$167.20
Purchase #4	$228.98	12.188%	$256.8881	$256.89	$256.90	$256.90
Purchase #5	$13.92	9.618%	$15.2588	$15.26	$15.25	$15.30
Purchase #6	$32.25	3.175%	$33.2739	$33.27	$33.25	$33.30
Purchase #7	$21.75	11.812%	$24.3191	$24.32	$24.30	$24.30
7 purchase totals =	$689.15		$751.7804	$751.79	$751.75	$751.80