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	$5.40	12.178%	$6.0576	$6.06	$6.05	$6.10
Purchase #2	$239.37	6.817%	$255.6879	$255.69	$255.70	$255.70
Purchase #3	$158.61	6.549%	$168.9974	$169.00	$169.00	$169.00
Purchase #4	$114.80	11.594%	$128.1099	$128.11	$128.10	$128.10
Purchase #5	$244.89	8.574%	$265.8869	$265.89	$265.90	$265.90
Purchase #6	$92.31	5.208%	$97.1175	$97.12	$97.10	$97.10
Purchase #7	$177.83	6.578%	$189.5277	$189.53	$189.55	$189.50
7 purchase totals =	$1,033.21		$1,111.3849	$1,111.40	$1,111.40	$1,111.40