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	$172.55	9.762%	$189.3943	$189.39	$189.40	$189.40
Purchase #2	$69.34	4.470%	$72.4395	$72.44	$72.45	$72.40
Purchase #3	$23.50	5.580%	$24.8113	$24.81	$24.80	$24.80
Purchase #4	$112.62	9.579%	$123.4079	$123.41	$123.40	$123.40
Purchase #5	$161.95	6.432%	$172.3666	$172.37	$172.35	$172.40
Purchase #6	$211.47	5.605%	$223.3229	$223.32	$223.30	$223.30
Purchase #7	$62.83	11.429%	$70.0108	$70.01	$70.00	$70.00
7 purchase totals =	$814.26		$875.7533	$875.75	$875.70	$875.70