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	$223.59	13.252%	$253.2201	$253.22	$253.20	$253.20
Purchase #2	$209.78	6.520%	$223.4577	$223.46	$223.45	$223.50
Purchase #3	$161.61	6.821%	$172.6334	$172.63	$172.65	$172.60
Purchase #4	$82.66	6.732%	$88.2247	$88.22	$88.20	$88.20
Purchase #5	$136.37	4.669%	$142.7371	$142.74	$142.75	$142.70
Purchase #6	$219.27	10.433%	$242.1464	$242.15	$242.15	$242.10
Purchase #7	$135.49	7.869%	$146.1517	$146.15	$146.15	$146.20
7 purchase totals =	$1,168.77		$1,268.5711	$1,268.57	$1,268.55	$1,268.50