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	$98.78	4.176%	$102.9051	$102.91	$102.90	$102.90
Purchase #2	$222.75	9.737%	$244.4392	$244.44	$244.45	$244.40
Purchase #3	$72.41	10.634%	$80.1101	$80.11	$80.10	$80.10
Purchase #4	$86.34	10.845%	$95.7036	$95.70	$95.70	$95.70
Purchase #5	$231.89	10.270%	$255.7051	$255.71	$255.70	$255.70
Purchase #6	$229.52	3.564%	$237.7001	$237.70	$237.70	$237.70
Purchase #7	$39.64	13.288%	$44.9074	$44.91	$44.90	$44.90
7 purchase totals =	$981.33		$1,061.4706	$1,061.48	$1,061.45	$1,061.40