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	$188.54	5.608%	$199.1133	$199.11	$199.10	$199.10
Purchase #2	$33.51	6.785%	$35.7837	$35.78	$35.80	$35.80
Purchase #3	$184.78	10.156%	$203.5463	$203.55	$203.55	$203.50
Purchase #4	$108.47	3.143%	$111.8792	$111.88	$111.90	$111.90
Purchase #5	$80.84	7.168%	$86.6346	$86.63	$86.65	$86.60
Purchase #6	$225.76	10.338%	$249.0991	$249.10	$249.10	$249.10
Purchase #7	$162.88	3.613%	$168.7649	$168.76	$168.75	$168.80
7 purchase totals =	$984.78		$1,054.8211	$1,054.81	$1,054.85	$1,054.80