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	$93.92	4.631%	$98.2694	$98.27	$98.25	$98.30
Purchase #2	$227.50	7.118%	$243.6935	$243.69	$243.70	$243.70
Purchase #3	$38.72	10.401%	$42.7473	$42.75	$42.75	$42.70
Purchase #4	$119.57	7.670%	$128.741	$128.74	$128.75	$128.70
Purchase #5	$231.74	10.174%	$255.3172	$255.32	$255.30	$255.30
Purchase #6	$94.52	9.667%	$103.6572	$103.66	$103.65	$103.70
Purchase #7	$160.32	9.441%	$175.4558	$175.46	$175.45	$175.50
7 purchase totals =	$966.29		$1,047.8814	$1,047.89	$1,047.85	$1,047.90