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	$167.38	8.862%	$182.2132	$182.21	$182.20	$182.20
Purchase #2	$160.76	11.792%	$179.7168	$179.72	$179.70	$179.70
Purchase #3	$181.60	7.317%	$194.8877	$194.89	$194.90	$194.90
Purchase #4	$57.29	3.672%	$59.3937	$59.39	$59.40	$59.40
Purchase #5	$205.85	4.359%	$214.823	$214.82	$214.80	$214.80
Purchase #6	$216.61	11.164%	$240.7923	$240.79	$240.80	$240.80
Purchase #7	$59.55	11.714%	$66.5257	$66.53	$66.55	$66.50
7 purchase totals =	$1,049.04		$1,138.3524	$1,138.35	$1,138.35	$1,138.30