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	$144.63	7.415%	$155.3543	$155.35	$155.35	$155.40
Purchase #2	$167.51	13.117%	$189.4823	$189.48	$189.50	$189.50
Purchase #3	$61.78	10.140%	$68.0445	$68.04	$68.05	$68.00
Purchase #4	$44.83	6.164%	$47.5933	$47.59	$47.60	$47.60
Purchase #5	$35.89	5.522%	$37.8718	$37.87	$37.85	$37.90
Purchase #6	$67.41	9.582%	$73.8692	$73.87	$73.85	$73.90
Purchase #7	$52.82	12.615%	$59.4832	$59.48	$59.50	$59.50
7 purchase totals =	$574.87		$631.6986	$631.68	$631.70	$631.80