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	$148.71	13.586%	$168.9137	$168.91	$168.90	$168.90
Purchase #2	$68.29	11.301%	$76.0075	$76.01	$76.00	$76.00
Purchase #3	$34.27	8.585%	$37.2121	$37.21	$37.20	$37.20
Purchase #4	$141.49	12.773%	$159.5625	$159.56	$159.55	$159.60
Purchase #5	$176.25	13.767%	$200.5143	$200.51	$200.50	$200.50
Purchase #6	$136.99	4.196%	$142.7381	$142.74	$142.75	$142.70
Purchase #7	$56.88	9.112%	$62.0629	$62.06	$62.05	$62.10
7 purchase totals =	$762.88		$847.0111	$847.00	$846.95	$847.00