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	$184.43	8.551%	$200.2006	$200.20	$200.20	$200.20
Purchase #2	$140.71	7.522%	$151.2942	$151.29	$151.30	$151.30
Purchase #3	$28.71	11.300%	$31.9542	$31.95	$31.95	$32.00
Purchase #4	$157.70	8.613%	$171.2827	$171.28	$171.30	$171.30
Purchase #5	$89.58	11.155%	$99.5726	$99.57	$99.55	$99.60
Purchase #6	$220.34	3.667%	$228.4199	$228.42	$228.40	$228.40
Purchase #7	$42.85	11.393%	$47.7319	$47.73	$47.75	$47.70
7 purchase totals =	$864.32		$930.4561	$930.44	$930.45	$930.50