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	$209.52	6.243%	$222.6003	$222.60	$222.60	$222.60
Purchase #2	$131.57	12.485%	$147.9965	$148.00	$148.00	$148.00
Purchase #3	$45.90	6.790%	$49.0166	$49.02	$49.00	$49.00
Purchase #4	$214.35	5.657%	$226.4758	$226.48	$226.50	$226.50
Purchase #5	$119.50	11.506%	$133.2497	$133.25	$133.25	$133.20
Purchase #6	$136.28	4.604%	$142.5543	$142.55	$142.55	$142.60
Purchase #7	$114.47	7.869%	$123.4776	$123.48	$123.50	$123.50
7 purchase totals =	$971.59		$1,045.3708	$1,045.38	$1,045.40	$1,045.40