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	$75.63	12.458%	$85.052	$85.05	$85.05	$85.10
Purchase #2	$194.67	6.279%	$206.8933	$206.89	$206.90	$206.90
Purchase #3	$246.80	4.470%	$257.832	$257.83	$257.85	$257.80
Purchase #4	$104.79	5.421%	$110.4707	$110.47	$110.45	$110.50
Purchase #5	$230.38	10.706%	$255.0445	$255.04	$255.05	$255.00
Purchase #6	$118.69	10.763%	$131.4646	$131.46	$131.45	$131.50
Purchase #7	$6.76	11.374%	$7.5289	$7.53	$7.55	$7.50
7 purchase totals =	$977.72		$1,054.2860	$1,054.27	$1,054.30	$1,054.30