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	$59.77	3.530%	$61.8799	$61.88	$61.90	$61.90
Purchase #2	$59.61	9.249%	$65.1233	$65.12	$65.10	$65.10
Purchase #3	$225.46	6.831%	$240.8612	$240.86	$240.85	$240.90
Purchase #4	$100.46	4.830%	$105.3122	$105.31	$105.30	$105.30
Purchase #5	$113.81	3.547%	$117.8468	$117.85	$117.85	$117.80
Purchase #6	$175.64	7.661%	$189.0958	$189.10	$189.10	$189.10
Purchase #7	$144.58	3.598%	$149.782	$149.78	$149.80	$149.80
7 purchase totals =	$879.33		$929.9012	$929.90	$929.90	$929.90