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	$184.55	8.583%	$200.3899	$200.39	$200.40	$200.40
Purchase #2	$151.37	6.717%	$161.5375	$161.54	$161.55	$161.50
Purchase #3	$193.28	11.789%	$216.0658	$216.07	$216.05	$216.10
Purchase #4	$80.51	11.349%	$89.6471	$89.65	$89.65	$89.60
Purchase #5	$120.26	9.661%	$131.8783	$131.88	$131.90	$131.90
Purchase #6	$94.72	9.865%	$104.0641	$104.06	$104.05	$104.10
Purchase #7	$148.69	7.394%	$159.6841	$159.68	$159.70	$159.70
7 purchase totals =	$973.38		$1,063.2668	$1,063.27	$1,063.30	$1,063.30