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	$246.61	9.434%	$269.8752	$269.88	$269.90	$269.90
Purchase #2	$62.91	12.432%	$70.731	$70.73	$70.75	$70.70
Purchase #3	$48.33	6.691%	$51.5638	$51.56	$51.55	$51.60
Purchase #4	$189.26	13.817%	$215.4101	$215.41	$215.40	$215.40
Purchase #5	$75.53	7.425%	$81.1381	$81.14	$81.15	$81.10
Purchase #6	$59.85	11.142%	$66.5185	$66.52	$66.50	$66.50
Purchase #7	$245.34	8.761%	$266.8342	$266.83	$266.85	$266.80
7 purchase totals =	$927.83		$1,022.0709	$1,022.07	$1,022.10	$1,022.00