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	$86.74	6.518%	$92.3937	$92.39	$92.40	$92.40
Purchase #2	$141.82	7.342%	$152.2324	$152.23	$152.25	$152.20
Purchase #3	$204.58	9.403%	$223.8167	$223.82	$223.80	$223.80
Purchase #4	$245.44	11.593%	$273.8939	$273.89	$273.90	$273.90
Purchase #5	$91.90	9.292%	$100.4393	$100.44	$100.45	$100.40
Purchase #6	$119.29	5.350%	$125.672	$125.67	$125.65	$125.70
Purchase #7	$72.94	10.146%	$80.3405	$80.34	$80.35	$80.30
7 purchase totals =	$962.71		$1,048.7885	$1,048.78	$1,048.80	$1,048.70