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	$186.29	5.615%	$196.7502	$196.75	$196.75	$196.80
Purchase #2	$223.69	8.748%	$243.2584	$243.26	$243.25	$243.30
Purchase #3	$116.85	13.661%	$132.8129	$132.81	$132.80	$132.80
Purchase #4	$48.81	3.187%	$50.3656	$50.37	$50.35	$50.40
Purchase #5	$176.97	7.211%	$189.7313	$189.73	$189.75	$189.70
Purchase #6	$10.63	12.139%	$11.9204	$11.92	$11.90	$11.90
Purchase #7	$244.87	11.689%	$273.4929	$273.49	$273.50	$273.50
7 purchase totals =	$1,008.11		$1,098.3317	$1,098.33	$1,098.30	$1,098.40