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	$122.63	3.776%	$127.2605	$127.26	$127.25	$127.30
Purchase #2	$125.55	8.253%	$135.9116	$135.91	$135.90	$135.90
Purchase #3	$156.52	9.671%	$171.657	$171.66	$171.65	$171.70
Purchase #4	$211.74	9.233%	$231.29	$231.29	$231.30	$231.30
Purchase #5	$250.62	5.294%	$263.8878	$263.89	$263.90	$263.90
Purchase #6	$54.43	9.103%	$59.3848	$59.38	$59.40	$59.40
Purchase #7	$12.86	8.306%	$13.9282	$13.93	$13.95	$13.90
7 purchase totals =	$934.35		$1,003.3199	$1,003.32	$1,003.35	$1,003.40