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	$48.44	5.762%	$51.2311	$51.23	$51.25	$51.20
Purchase #2	$212.62	5.848%	$225.054	$225.05	$225.05	$225.10
Purchase #3	$238.59	5.239%	$251.0897	$251.09	$251.10	$251.10
Purchase #4	$242.96	8.626%	$263.9177	$263.92	$263.90	$263.90
Purchase #5	$71.27	10.483%	$78.7412	$78.74	$78.75	$78.70
Purchase #6	$157.31	6.690%	$167.834	$167.83	$167.85	$167.80
Purchase #7	$43.76	11.155%	$48.6414	$48.64	$48.65	$48.60
7 purchase totals =	$1,014.95		$1,086.5091	$1,086.50	$1,086.55	$1,086.40