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	$150.55	4.360%	$157.114	$157.11	$157.10	$157.10
Purchase #2	$199.84	11.548%	$222.9175	$222.92	$222.90	$222.90
Purchase #3	$116.81	12.282%	$131.1566	$131.16	$131.15	$131.20
Purchase #4	$81.95	9.790%	$89.9729	$89.97	$89.95	$90.00
Purchase #5	$73.44	12.466%	$82.595	$82.60	$82.60	$82.60
Purchase #6	$238.93	10.726%	$264.5576	$264.56	$264.55	$264.60
Purchase #7	$162.60	10.457%	$179.6031	$179.60	$179.60	$179.60
7 purchase totals =	$1,024.12		$1,127.9167	$1,127.92	$1,127.85	$1,128.00