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	$124.44	4.421%	$129.9415	$129.94	$129.95	$129.90
Purchase #2	$227.54	12.503%	$255.9893	$255.99	$256.00	$256.00
Purchase #3	$53.37	6.417%	$56.7948	$56.79	$56.80	$56.80
Purchase #4	$151.83	8.272%	$164.3894	$164.39	$164.40	$164.40
Purchase #5	$245.92	7.819%	$265.1485	$265.15	$265.15	$265.10
Purchase #6	$84.28	6.683%	$89.9124	$89.91	$89.90	$89.90
Purchase #7	$167.54	13.586%	$190.302	$190.30	$190.30	$190.30
7 purchase totals =	$1,054.92		$1,152.4779	$1,152.47	$1,152.50	$1,152.40