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	$185.78	10.179%	$204.6905	$204.69	$204.70	$204.70
Purchase #2	$133.76	12.804%	$150.8866	$150.89	$150.90	$150.90
Purchase #3	$77.57	7.699%	$83.5421	$83.54	$83.55	$83.50
Purchase #4	$76.99	4.425%	$80.3968	$80.40	$80.40	$80.40
Purchase #5	$40.63	10.417%	$44.8624	$44.86	$44.85	$44.90
Purchase #6	$198.54	8.806%	$216.0234	$216.02	$216.00	$216.00
Purchase #7	$27.46	3.874%	$28.5238	$28.52	$28.50	$28.50
7 purchase totals =	$740.73		$808.9256	$808.92	$808.90	$808.90