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	$79.36	7.378%	$85.2152	$85.22	$85.20	$85.20
Purchase #2	$42.29	6.677%	$45.1137	$45.11	$45.10	$45.10
Purchase #3	$7.55	7.588%	$8.1229	$8.12	$8.10	$8.10
Purchase #4	$186.85	11.649%	$208.6162	$208.62	$208.60	$208.60
Purchase #5	$177.60	4.453%	$185.5085	$185.51	$185.50	$185.50
Purchase #6	$231.42	10.405%	$255.4993	$255.50	$255.50	$255.50
Purchase #7	$217.63	4.612%	$227.6671	$227.67	$227.65	$227.70
7 purchase totals =	$942.70		$1,015.7429	$1,015.75	$1,015.65	$1,015.70