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	$58.43	11.411%	$65.0974	$65.10	$65.10	$65.10
Purchase #2	$217.76	10.628%	$240.9035	$240.90	$240.90	$240.90
Purchase #3	$84.46	11.563%	$94.2261	$94.23	$94.25	$94.20
Purchase #4	$205.62	4.633%	$215.1464	$215.15	$215.15	$215.10
Purchase #5	$158.40	9.145%	$172.8857	$172.89	$172.90	$172.90
Purchase #6	$225.61	12.510%	$253.8338	$253.83	$253.85	$253.80
Purchase #7	$31.28	12.220%	$35.1024	$35.10	$35.10	$35.10
7 purchase totals =	$981.56		$1,077.1953	$1,077.20	$1,077.25	$1,077.10