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	$154.86	4.378%	$161.6398	$161.64	$161.65	$161.60
Purchase #2	$193.52	11.284%	$215.3568	$215.36	$215.35	$215.40
Purchase #3	$90.66	9.471%	$99.2464	$99.25	$99.25	$99.20
Purchase #4	$77.59	4.620%	$81.1747	$81.17	$81.15	$81.20
Purchase #5	$240.68	7.381%	$258.4446	$258.44	$258.45	$258.40
Purchase #6	$83.45	7.398%	$89.6236	$89.62	$89.60	$89.60
Purchase #7	$232.90	13.118%	$263.4518	$263.45	$263.45	$263.50
7 purchase totals =	$1,073.66		$1,168.9377	$1,168.93	$1,168.90	$1,168.90