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	$159.39	13.480%	$180.8758	$180.88	$180.90	$180.90
Purchase #2	$100.92	4.520%	$105.4816	$105.48	$105.50	$105.50
Purchase #3	$153.32	11.711%	$171.2753	$171.28	$171.30	$171.30
Purchase #4	$220.40	5.562%	$232.6586	$232.66	$232.65	$232.70
Purchase #5	$237.52	8.145%	$256.866	$256.87	$256.85	$256.90
Purchase #6	$68.32	4.328%	$71.2769	$71.28	$71.30	$71.30
Purchase #7	$58.41	9.129%	$63.7422	$63.74	$63.75	$63.70
7 purchase totals =	$998.28		$1,082.1764	$1,082.19	$1,082.25	$1,082.30