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	$163.59	7.537%	$175.9198	$175.92	$175.90	$175.90
Purchase #2	$9.71	10.590%	$10.7383	$10.74	$10.75	$10.70
Purchase #3	$149.30	10.425%	$164.8645	$164.86	$164.85	$164.90
Purchase #4	$197.90	13.245%	$224.1119	$224.11	$224.10	$224.10
Purchase #5	$57.99	13.650%	$65.9056	$65.91	$65.90	$65.90
Purchase #6	$78.86	11.762%	$88.1355	$88.14	$88.15	$88.10
Purchase #7	$39.37	8.815%	$42.8405	$42.84	$42.85	$42.80
7 purchase totals =	$696.72		$772.5161	$772.52	$772.50	$772.40