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	$141.88	4.519%	$148.2916	$148.29	$148.30	$148.30
Purchase #2	$155.96	10.848%	$172.8785	$172.88	$172.90	$172.90
Purchase #3	$72.92	13.376%	$82.6738	$82.67	$82.65	$82.70
Purchase #4	$244.86	5.289%	$257.8106	$257.81	$257.80	$257.80
Purchase #5	$165.92	3.645%	$171.9678	$171.97	$171.95	$172.00
Purchase #6	$63.56	10.487%	$70.2255	$70.23	$70.25	$70.20
Purchase #7	$116.27	3.507%	$120.3476	$120.35	$120.35	$120.30
7 purchase totals =	$961.37		$1,024.1954	$1,024.20	$1,024.20	$1,024.20