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	$140.60	4.497%	$146.9228	$146.92	$146.90	$146.90
Purchase #2	$178.88	13.869%	$203.6889	$203.69	$203.70	$203.70
Purchase #3	$25.32	13.459%	$28.7278	$28.73	$28.75	$28.70
Purchase #4	$143.45	13.346%	$162.5948	$162.59	$162.60	$162.60
Purchase #5	$64.52	3.578%	$66.8285	$66.83	$66.85	$66.80
Purchase #6	$242.29	9.646%	$265.6613	$265.66	$265.65	$265.70
Purchase #7	$140.58	3.826%	$145.9586	$145.96	$145.95	$146.00
7 purchase totals =	$935.64		$1,020.3827	$1,020.38	$1,020.40	$1,020.40