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	$144.33	4.500%	$150.8249	$150.82	$150.80	$150.80
Purchase #2	$19.46	5.692%	$20.5677	$20.57	$20.55	$20.60
Purchase #3	$173.52	9.570%	$190.1259	$190.13	$190.15	$190.10
Purchase #4	$122.93	10.744%	$136.1376	$136.14	$136.15	$136.10
Purchase #5	$235.50	3.175%	$242.9771	$242.98	$243.00	$243.00
Purchase #6	$142.61	12.770%	$160.8213	$160.82	$160.80	$160.80
Purchase #7	$232.83	4.560%	$243.447	$243.45	$243.45	$243.40
7 purchase totals =	$1,071.18		$1,144.9015	$1,144.91	$1,144.90	$1,144.80