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	$127.53	3.348%	$131.7997	$131.80	$131.80	$131.80
Purchase #2	$20.30	7.758%	$21.8749	$21.87	$21.85	$21.90
Purchase #3	$63.37	4.743%	$66.3756	$66.38	$66.40	$66.40
Purchase #4	$28.85	5.612%	$30.4691	$30.47	$30.45	$30.50
Purchase #5	$181.55	6.588%	$193.5105	$193.51	$193.50	$193.50
Purchase #6	$122.42	9.380%	$133.903	$133.90	$133.90	$133.90
Purchase #7	$71.84	6.113%	$76.2316	$76.23	$76.25	$76.20
7 purchase totals =	$615.86		$654.1644	$654.16	$654.15	$654.20