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	$158.82	9.827%	$174.4272	$174.43	$174.45	$174.40
Purchase #2	$203.78	10.740%	$225.666	$225.67	$225.65	$225.70
Purchase #3	$92.78	6.332%	$98.6548	$98.65	$98.65	$98.70
Purchase #4	$76.49	12.767%	$86.2555	$86.26	$86.25	$86.30
Purchase #5	$108.60	13.774%	$123.5586	$123.56	$123.55	$123.60
Purchase #6	$95.66	3.333%	$98.8483	$98.85	$98.85	$98.80
Purchase #7	$12.44	11.753%	$13.9021	$13.90	$13.90	$13.90
7 purchase totals =	$748.57		$821.3125	$821.32	$821.30	$821.40