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	$151.43	3.843%	$157.2495	$157.25	$157.25	$157.20
Purchase #2	$240.83	9.476%	$263.6511	$263.65	$263.65	$263.70
Purchase #3	$100.56	5.158%	$105.7469	$105.75	$105.75	$105.70
Purchase #4	$215.37	8.384%	$233.4266	$233.43	$233.45	$233.40
Purchase #5	$94.78	10.482%	$104.7148	$104.71	$104.70	$104.70
Purchase #6	$170.30	10.122%	$187.5378	$187.54	$187.55	$187.50
Purchase #7	$87.83	3.822%	$91.1869	$91.19	$91.20	$91.20
7 purchase totals =	$1,061.10		$1,143.5136	$1,143.52	$1,143.55	$1,143.40