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	$109.78	13.769%	$124.8956	$124.90	$124.90	$124.90
Purchase #2	$59.74	13.259%	$67.6609	$67.66	$67.65	$67.70
Purchase #3	$50.63	3.339%	$52.3205	$52.32	$52.30	$52.30
Purchase #4	$81.81	13.391%	$92.7652	$92.77	$92.75	$92.80
Purchase #5	$164.74	4.112%	$171.5141	$171.51	$171.50	$171.50
Purchase #6	$50.46	6.595%	$53.7878	$53.79	$53.80	$53.80
Purchase #7	$124.54	13.322%	$141.1312	$141.13	$141.15	$141.10
7 purchase totals =	$641.70		$704.0753	$704.08	$704.05	$704.10