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	$38.78	4.199%	$40.4084	$40.41	$40.40	$40.40
Purchase #2	$21.65	5.456%	$22.8312	$22.83	$22.85	$22.80
Purchase #3	$200.72	7.716%	$216.2076	$216.21	$216.20	$216.20
Purchase #4	$109.64	7.201%	$117.5352	$117.54	$117.55	$117.50
Purchase #5	$201.53	4.229%	$210.0527	$210.05	$210.05	$210.10
Purchase #6	$45.61	11.442%	$50.8287	$50.83	$50.85	$50.80
Purchase #7	$134.46	11.851%	$150.3949	$150.39	$150.40	$150.40
7 purchase totals =	$752.39		$808.2587	$808.26	$808.30	$808.20