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	$145.40	4.161%	$151.4501	$151.45	$151.45	$151.50
Purchase #2	$156.25	6.341%	$166.1578	$166.16	$166.15	$166.20
Purchase #3	$73.98	9.271%	$80.8387	$80.84	$80.85	$80.80
Purchase #4	$203.26	6.589%	$216.6528	$216.65	$216.65	$216.70
Purchase #5	$63.28	7.298%	$67.8982	$67.90	$67.90	$67.90
Purchase #6	$129.52	3.130%	$133.574	$133.57	$133.55	$133.60
Purchase #7	$219.69	11.280%	$244.471	$244.47	$244.45	$244.50
7 purchase totals =	$991.38		$1,061.0426	$1,061.04	$1,061.00	$1,061.20