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	$83.86	12.743%	$94.5463	$94.55	$94.55	$94.50
Purchase #2	$168.56	9.168%	$184.0136	$184.01	$184.00	$184.00
Purchase #3	$50.48	7.769%	$54.4018	$54.40	$54.40	$54.40
Purchase #4	$127.84	8.837%	$139.1372	$139.14	$139.15	$139.10
Purchase #5	$240.52	12.538%	$270.6764	$270.68	$270.70	$270.70
Purchase #6	$55.25	11.806%	$61.7728	$61.77	$61.75	$61.80
Purchase #7	$181.50	13.529%	$206.0551	$206.06	$206.05	$206.10
7 purchase totals =	$908.01		$1,010.6032	$1,010.61	$1,010.60	$1,010.60