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	$110.48	7.583%	$118.8577	$118.86	$118.85	$118.90
Purchase #2	$204.39	6.127%	$216.913	$216.91	$216.90	$216.90
Purchase #3	$43.37	5.371%	$45.6994	$45.70	$45.70	$45.70
Purchase #4	$106.90	10.437%	$118.0572	$118.06	$118.05	$118.10
Purchase #5	$175.82	9.446%	$192.428	$192.43	$192.45	$192.40
Purchase #6	$66.87	11.472%	$74.5413	$74.54	$74.55	$74.50
Purchase #7	$93.76	11.803%	$104.8265	$104.83	$104.85	$104.80
7 purchase totals =	$801.59		$871.3231	$871.33	$871.35	$871.30