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	$178.42	6.353%	$189.755	$189.76	$189.75	$189.80
Purchase #2	$5.27	5.430%	$5.5562	$5.56	$5.55	$5.60
Purchase #3	$225.35	3.434%	$233.0885	$233.09	$233.10	$233.10
Purchase #4	$71.86	9.715%	$78.8412	$78.84	$78.85	$78.80
Purchase #5	$51.50	6.191%	$54.6884	$54.69	$54.70	$54.70
Purchase #6	$192.56	8.155%	$208.2633	$208.26	$208.25	$208.30
Purchase #7	$248.50	9.420%	$271.9087	$271.91	$271.90	$271.90
7 purchase totals =	$973.46		$1,042.1013	$1,042.11	$1,042.10	$1,042.20