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	$226.55	7.188%	$242.8344	$242.83	$242.85	$242.80
Purchase #2	$71.91	7.663%	$77.4205	$77.42	$77.40	$77.40
Purchase #3	$77.86	3.379%	$80.4909	$80.49	$80.50	$80.50
Purchase #4	$248.51	7.411%	$266.9271	$266.93	$266.95	$266.90
Purchase #5	$48.79	10.554%	$53.9393	$53.94	$53.95	$53.90
Purchase #6	$165.29	4.593%	$172.8818	$172.88	$172.90	$172.90
Purchase #7	$152.44	6.507%	$162.3593	$162.36	$162.35	$162.40
7 purchase totals =	$991.35		$1,056.8533	$1,056.85	$1,056.90	$1,056.80