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	$68.82	4.620%	$71.9995	$72.00	$72.00	$72.00
Purchase #2	$182.63	6.538%	$194.5703	$194.57	$194.55	$194.60
Purchase #3	$228.43	9.627%	$250.421	$250.42	$250.40	$250.40
Purchase #4	$34.48	13.466%	$39.1231	$39.12	$39.10	$39.10
Purchase #5	$240.70	7.194%	$258.016	$258.02	$258.00	$258.00
Purchase #6	$179.62	6.204%	$190.7636	$190.76	$190.75	$190.80
Purchase #7	$159.86	6.232%	$169.8225	$169.82	$169.80	$169.80
7 purchase totals =	$1,094.54		$1,174.7160	$1,174.71	$1,174.60	$1,174.70