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	$33.95	4.169%	$35.3654	$35.37	$35.35	$35.40
Purchase #2	$33.42	12.714%	$37.669	$37.67	$37.65	$37.70
Purchase #3	$181.31	8.155%	$196.0958	$196.10	$196.10	$196.10
Purchase #4	$219.46	4.465%	$229.2589	$229.26	$229.25	$229.30
Purchase #5	$20.25	4.190%	$21.0985	$21.10	$21.10	$21.10
Purchase #6	$120.80	11.663%	$134.8889	$134.89	$134.90	$134.90
Purchase #7	$239.26	3.873%	$248.5265	$248.53	$248.55	$248.50
7 purchase totals =	$848.45		$902.9030	$902.92	$902.90	$903.00