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	$94.89	5.111%	$99.7398	$99.74	$99.75	$99.70
Purchase #2	$145.54	4.362%	$151.8885	$151.89	$151.90	$151.90
Purchase #3	$143.30	6.387%	$152.4526	$152.45	$152.45	$152.50
Purchase #4	$228.34	9.420%	$249.8496	$249.85	$249.85	$249.80
Purchase #5	$108.81	5.346%	$114.627	$114.63	$114.65	$114.60
Purchase #6	$168.75	12.498%	$189.8404	$189.84	$189.85	$189.80
Purchase #7	$143.27	3.198%	$147.8518	$147.85	$147.85	$147.90
7 purchase totals =	$1,032.90		$1,106.2497	$1,106.25	$1,106.30	$1,106.20