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	$30.67	9.267%	$33.5122	$33.51	$33.50	$33.50
Purchase #2	$82.26	4.798%	$86.2068	$86.21	$86.20	$86.20
Purchase #3	$155.71	12.377%	$174.9822	$174.98	$175.00	$175.00
Purchase #4	$121.46	4.594%	$127.0399	$127.04	$127.05	$127.00
Purchase #5	$187.57	4.637%	$196.2676	$196.27	$196.25	$196.30
Purchase #6	$177.33	7.551%	$190.7202	$190.72	$190.70	$190.70
Purchase #7	$11.66	6.345%	$12.3998	$12.40	$12.40	$12.40
7 purchase totals =	$766.66		$821.1287	$821.13	$821.10	$821.10