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	$179.54	9.476%	$196.5532	$196.55	$196.55	$196.60
Purchase #2	$165.33	10.124%	$182.068	$182.07	$182.05	$182.10
Purchase #3	$143.90	4.379%	$150.2014	$150.20	$150.20	$150.20
Purchase #4	$134.41	9.410%	$147.058	$147.06	$147.05	$147.10
Purchase #5	$143.31	4.865%	$150.282	$150.28	$150.30	$150.30
Purchase #6	$132.95	12.703%	$149.8386	$149.84	$149.85	$149.80
Purchase #7	$100.56	4.445%	$105.0299	$105.03	$105.05	$105.00
7 purchase totals =	$1,000.00		$1,081.0311	$1,081.03	$1,081.05	$1,081.10