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	$163.45	12.861%	$184.4713	$184.47	$184.45	$184.50
Purchase #2	$48.45	7.704%	$52.1826	$52.18	$52.20	$52.20
Purchase #3	$199.52	7.810%	$215.1025	$215.10	$215.10	$215.10
Purchase #4	$91.75	5.603%	$96.8908	$96.89	$96.90	$96.90
Purchase #5	$193.77	13.787%	$220.4851	$220.49	$220.50	$220.50
Purchase #6	$164.77	6.451%	$175.3993	$175.40	$175.40	$175.40
Purchase #7	$137.83	7.802%	$148.5835	$148.58	$148.60	$148.60
7 purchase totals =	$999.54		$1,093.1151	$1,093.11	$1,093.15	$1,093.20