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	$42.33	7.133%	$45.3494	$45.35	$45.35	$45.30
Purchase #2	$157.57	7.222%	$168.9497	$168.95	$168.95	$168.90
Purchase #3	$164.57	5.824%	$174.1546	$174.15	$174.15	$174.20
Purchase #4	$215.64	4.145%	$224.5783	$224.58	$224.60	$224.60
Purchase #5	$42.77	5.362%	$45.0633	$45.06	$45.05	$45.10
Purchase #6	$63.26	13.585%	$71.8539	$71.85	$71.85	$71.90
Purchase #7	$206.95	4.143%	$215.5239	$215.52	$215.50	$215.50
7 purchase totals =	$893.09		$945.4731	$945.46	$945.45	$945.50