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	$146.36	11.843%	$163.6934	$163.69	$163.70	$163.70
Purchase #2	$96.53	7.545%	$103.8132	$103.81	$103.80	$103.80
Purchase #3	$54.59	11.738%	$60.9978	$61.00	$61.00	$61.00
Purchase #4	$86.47	4.640%	$90.4822	$90.48	$90.50	$90.50
Purchase #5	$55.44	7.519%	$59.6085	$59.61	$59.60	$59.60
Purchase #6	$209.58	4.269%	$218.527	$218.53	$218.55	$218.50
Purchase #7	$183.37	10.581%	$202.7724	$202.77	$202.75	$202.80
7 purchase totals =	$832.34		$899.8945	$899.89	$899.90	$899.90