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	$90.97	6.694%	$97.0595	$97.06	$97.05	$97.10
Purchase #2	$95.55	6.676%	$101.9289	$101.93	$101.95	$101.90
Purchase #3	$224.44	4.510%	$234.5622	$234.56	$234.55	$234.60
Purchase #4	$239.86	4.283%	$250.1332	$250.13	$250.15	$250.10
Purchase #5	$157.78	4.504%	$164.8864	$164.89	$164.90	$164.90
Purchase #6	$172.69	4.316%	$180.1433	$180.14	$180.15	$180.10
Purchase #7	$126.96	12.385%	$142.684	$142.68	$142.70	$142.70
7 purchase totals =	$1,108.25		$1,171.3975	$1,171.39	$1,171.45	$1,171.40