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	$122.72	3.822%	$127.4104	$127.41	$127.40	$127.40
Purchase #2	$119.59	9.540%	$130.9989	$131.00	$131.00	$131.00
Purchase #3	$128.46	6.404%	$136.6866	$136.69	$136.70	$136.70
Purchase #4	$31.92	4.644%	$33.4024	$33.40	$33.40	$33.40
Purchase #5	$226.82	8.785%	$246.7461	$246.75	$246.75	$246.70
Purchase #6	$172.98	8.866%	$188.3164	$188.32	$188.30	$188.30
Purchase #7	$198.57	7.563%	$213.5878	$213.59	$213.60	$213.60
7 purchase totals =	$1,001.06		$1,077.1486	$1,077.16	$1,077.15	$1,077.10