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	$64.66	12.443%	$72.7056	$72.71	$72.70	$72.70
Purchase #2	$204.69	10.429%	$226.0371	$226.04	$226.05	$226.00
Purchase #3	$98.90	7.185%	$106.006	$106.01	$106.00	$106.00
Purchase #4	$214.47	3.625%	$222.2445	$222.24	$222.25	$222.20
Purchase #5	$248.52	7.496%	$267.1491	$267.15	$267.15	$267.10
Purchase #6	$74.71	10.194%	$82.3259	$82.33	$82.35	$82.30
Purchase #7	$87.60	8.522%	$95.0653	$95.07	$95.05	$95.10
7 purchase totals =	$993.55		$1,071.5335	$1,071.55	$1,071.55	$1,071.40