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	$209.66	10.846%	$232.3997	$232.40	$232.40	$232.40
Purchase #2	$235.64	12.468%	$265.0196	$265.02	$265.00	$265.00
Purchase #3	$238.86	12.620%	$269.0041	$269.00	$269.00	$269.00
Purchase #4	$90.83	6.788%	$96.9955	$97.00	$97.00	$97.00
Purchase #5	$122.66	13.766%	$139.5454	$139.55	$139.55	$139.50
Purchase #6	$17.68	13.297%	$20.0309	$20.03	$20.05	$20.00
Purchase #7	$159.31	8.663%	$173.111	$173.11	$173.10	$173.10
7 purchase totals =	$1,074.64		$1,196.1062	$1,196.11	$1,196.10	$1,196.00