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	$163.32	3.776%	$169.487	$169.49	$169.50	$169.50
Purchase #2	$75.77	4.624%	$79.2736	$79.27	$79.25	$79.30
Purchase #3	$81.58	9.406%	$89.2534	$89.25	$89.25	$89.30
Purchase #4	$205.98	11.310%	$229.2763	$229.28	$229.30	$229.30
Purchase #5	$179.42	13.174%	$203.0568	$203.06	$203.05	$203.10
Purchase #6	$188.27	6.490%	$200.4887	$200.49	$200.50	$200.50
Purchase #7	$136.59	11.345%	$152.0861	$152.09	$152.10	$152.10
7 purchase totals =	$1,030.93		$1,122.9219	$1,122.93	$1,122.95	$1,123.10