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	$54.96	8.638%	$59.7074	$59.71	$59.70	$59.70
Purchase #2	$213.97	6.771%	$228.4579	$228.46	$228.45	$228.50
Purchase #3	$147.69	10.325%	$162.939	$162.94	$162.95	$162.90
Purchase #4	$219.64	6.199%	$233.2555	$233.26	$233.25	$233.30
Purchase #5	$44.70	4.853%	$46.8693	$46.87	$46.85	$46.90
Purchase #6	$214.47	6.694%	$228.8266	$228.83	$228.85	$228.80
Purchase #7	$208.85	10.156%	$230.0608	$230.06	$230.05	$230.10
7 purchase totals =	$1,104.28		$1,190.1165	$1,190.13	$1,190.10	$1,190.20