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	$83.54	12.577%	$94.0468	$94.05	$94.05	$94.00
Purchase #2	$78.40	9.201%	$85.6136	$85.61	$85.60	$85.60
Purchase #3	$48.65	9.559%	$53.3005	$53.30	$53.30	$53.30
Purchase #4	$188.25	4.438%	$196.6045	$196.60	$196.60	$196.60
Purchase #5	$134.84	4.640%	$141.0966	$141.10	$141.10	$141.10
Purchase #6	$75.56	4.495%	$78.9564	$78.96	$78.95	$79.00
Purchase #7	$48.57	5.106%	$51.05	$51.05	$51.05	$51.10
7 purchase totals =	$657.81		$700.6684	$700.67	$700.65	$700.70