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	$12.95	9.855%	$14.2262	$14.23	$14.25	$14.20
Purchase #2	$248.90	8.444%	$269.9171	$269.92	$269.90	$269.90
Purchase #3	$188.89	11.663%	$210.9202	$210.92	$210.90	$210.90
Purchase #4	$155.30	8.296%	$168.1837	$168.18	$168.20	$168.20
Purchase #5	$83.46	7.258%	$89.5175	$89.52	$89.50	$89.50
Purchase #6	$163.80	5.232%	$172.37	$172.37	$172.35	$172.40
Purchase #7	$215.69	13.221%	$244.2064	$244.21	$244.20	$244.20
7 purchase totals =	$1,068.99		$1,169.3411	$1,169.35	$1,169.30	$1,169.30