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	$242.95	4.828%	$254.6796	$254.68	$254.70	$254.70
Purchase #2	$102.32	6.703%	$109.1785	$109.18	$109.20	$109.20
Purchase #3	$48.32	12.199%	$54.2146	$54.21	$54.20	$54.20
Purchase #4	$176.91	12.707%	$199.39	$199.39	$199.40	$199.40
Purchase #5	$112.82	3.537%	$116.8104	$116.81	$116.80	$116.80
Purchase #6	$229.39	10.357%	$253.1479	$253.15	$253.15	$253.10
Purchase #7	$90.36	8.800%	$98.3117	$98.31	$98.30	$98.30
7 purchase totals =	$1,003.07		$1,085.7327	$1,085.73	$1,085.75	$1,085.70