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	$141.68	7.408%	$152.1757	$152.18	$152.20	$152.20
Purchase #2	$41.82	8.797%	$45.4989	$45.50	$45.50	$45.50
Purchase #3	$241.62	9.330%	$264.1631	$264.16	$264.15	$264.20
Purchase #4	$37.72	13.836%	$42.9389	$42.94	$42.95	$42.90
Purchase #5	$181.40	9.408%	$198.4661	$198.47	$198.45	$198.50
Purchase #6	$203.72	13.465%	$231.1509	$231.15	$231.15	$231.20
Purchase #7	$92.35	8.804%	$100.4805	$100.48	$100.50	$100.50
7 purchase totals =	$940.31		$1,034.8741	$1,034.88	$1,034.90	$1,035.00