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	$65.53	9.640%	$71.8471	$71.85	$71.85	$71.80
Purchase #2	$139.43	13.540%	$158.3088	$158.31	$158.30	$158.30
Purchase #3	$76.78	8.750%	$83.4983	$83.50	$83.50	$83.50
Purchase #4	$170.53	6.215%	$181.1284	$181.13	$181.15	$181.10
Purchase #5	$64.71	5.267%	$68.1183	$68.12	$68.10	$68.10
Purchase #6	$10.38	3.380%	$10.7308	$10.73	$10.75	$10.70
Purchase #7	$207.37	3.823%	$215.2978	$215.30	$215.30	$215.30
7 purchase totals =	$734.73		$788.9295	$788.94	$788.95	$788.80