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	$81.50	4.567%	$85.2221	$85.22	$85.20	$85.20
Purchase #2	$26.30	7.502%	$28.273	$28.27	$28.25	$28.30
Purchase #3	$47.28	8.590%	$51.3414	$51.34	$51.35	$51.30
Purchase #4	$105.47	3.408%	$109.0644	$109.06	$109.05	$109.10
Purchase #5	$157.53	13.213%	$178.3444	$178.34	$178.35	$178.30
Purchase #6	$140.66	11.439%	$156.7501	$156.75	$156.75	$156.80
Purchase #7	$142.84	5.639%	$150.8947	$150.89	$150.90	$150.90
7 purchase totals =	$701.58		$759.8901	$759.87	$759.85	$759.90