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	$48.85	11.672%	$54.5518	$54.55	$54.55	$54.60
Purchase #2	$177.61	9.292%	$194.1135	$194.11	$194.10	$194.10
Purchase #3	$131.35	8.700%	$142.7775	$142.78	$142.80	$142.80
Purchase #4	$31.66	13.281%	$35.8648	$35.86	$35.85	$35.90
Purchase #5	$220.59	7.436%	$236.9931	$236.99	$237.00	$237.00
Purchase #6	$185.72	11.397%	$206.8865	$206.89	$206.90	$206.90
Purchase #7	$55.78	7.493%	$59.9596	$59.96	$59.95	$60.00
7 purchase totals =	$851.56		$931.1468	$931.14	$931.15	$931.30