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	$59.75	10.109%	$65.7901	$65.79	$65.80	$65.80
Purchase #2	$204.57	8.563%	$222.0873	$222.09	$222.10	$222.10
Purchase #3	$6.80	12.254%	$7.6333	$7.63	$7.65	$7.60
Purchase #4	$174.61	3.252%	$180.2883	$180.29	$180.30	$180.30
Purchase #5	$203.28	9.346%	$222.2785	$222.28	$222.30	$222.30
Purchase #6	$206.81	10.638%	$228.8104	$228.81	$228.80	$228.80
Purchase #7	$247.85	10.370%	$273.552	$273.55	$273.55	$273.60
7 purchase totals =	$1,103.67		$1,200.4399	$1,200.44	$1,200.50	$1,200.50