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	$198.97	10.462%	$219.7862	$219.79	$219.80	$219.80
Purchase #2	$30.82	10.597%	$34.086	$34.09	$34.10	$34.10
Purchase #3	$26.65	6.196%	$28.3012	$28.30	$28.30	$28.30
Purchase #4	$183.43	12.435%	$206.2395	$206.24	$206.25	$206.20
Purchase #5	$237.45	7.687%	$255.7028	$255.70	$255.70	$255.70
Purchase #6	$85.86	4.251%	$89.5099	$89.51	$89.50	$89.50
Purchase #7	$170.50	7.287%	$182.9243	$182.92	$182.90	$182.90
7 purchase totals =	$933.68		$1,016.5499	$1,016.55	$1,016.55	$1,016.50