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	$232.72	6.438%	$247.7025	$247.70	$247.70	$247.70
Purchase #2	$139.95	11.250%	$155.6944	$155.69	$155.70	$155.70
Purchase #3	$184.54	11.565%	$205.8821	$205.88	$205.90	$205.90
Purchase #4	$151.86	13.473%	$172.3201	$172.32	$172.30	$172.30
Purchase #5	$20.60	4.862%	$21.6016	$21.60	$21.60	$21.60
Purchase #6	$174.90	13.706%	$198.8718	$198.87	$198.85	$198.90
Purchase #7	$55.75	4.202%	$58.0926	$58.09	$58.10	$58.10
7 purchase totals =	$960.32		$1,060.1651	$1,060.15	$1,060.15	$1,060.20