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	$223.65	3.528%	$231.5404	$231.54	$231.55	$231.50
Purchase #2	$219.86	7.820%	$237.0531	$237.05	$237.05	$237.10
Purchase #3	$73.39	11.755%	$82.017	$82.02	$82.00	$82.00
Purchase #4	$99.50	3.848%	$103.3288	$103.33	$103.35	$103.30
Purchase #5	$89.53	4.371%	$93.4434	$93.44	$93.45	$93.40
Purchase #6	$135.75	10.706%	$150.2834	$150.28	$150.30	$150.30
Purchase #7	$158.83	9.417%	$173.787	$173.79	$173.80	$173.80
7 purchase totals =	$1,000.51		$1,071.4531	$1,071.45	$1,071.50	$1,071.40