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	$151.88	11.867%	$169.9036	$169.90	$169.90	$169.90
Purchase #2	$94.57	6.806%	$101.0064	$101.01	$101.00	$101.00
Purchase #3	$248.82	11.195%	$276.6754	$276.68	$276.70	$276.70
Purchase #4	$219.36	11.822%	$245.2927	$245.29	$245.30	$245.30
Purchase #5	$66.34	12.779%	$74.8176	$74.82	$74.80	$74.80
Purchase #6	$37.82	12.650%	$42.6042	$42.60	$42.60	$42.60
Purchase #7	$90.92	9.662%	$99.7047	$99.70	$99.70	$99.70
7 purchase totals =	$909.71		$1,010.0046	$1,010.00	$1,010.00	$1,010.00