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	$202.78	4.277%	$211.4529	$211.45	$211.45	$211.50
Purchase #2	$157.45	4.783%	$164.9808	$164.98	$165.00	$165.00
Purchase #3	$163.62	13.460%	$185.6433	$185.64	$185.65	$185.60
Purchase #4	$238.85	4.730%	$250.1476	$250.15	$250.15	$250.10
Purchase #5	$210.27	11.174%	$233.7656	$233.77	$233.75	$233.80
Purchase #6	$72.97	6.172%	$77.4737	$77.47	$77.45	$77.50
Purchase #7	$75.36	10.820%	$83.514	$83.51	$83.50	$83.50
7 purchase totals =	$1,121.30		$1,206.9779	$1,206.97	$1,206.95	$1,207.00