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	$186.45	3.144%	$192.312	$192.31	$192.30	$192.30
Purchase #2	$29.28	11.293%	$32.5866	$32.59	$32.60	$32.60
Purchase #3	$201.55	10.584%	$222.8821	$222.88	$222.90	$222.90
Purchase #4	$160.26	4.468%	$167.4204	$167.42	$167.40	$167.40
Purchase #5	$201.70	12.610%	$227.1344	$227.13	$227.15	$227.10
Purchase #6	$220.32	9.284%	$240.7745	$240.77	$240.75	$240.80
Purchase #7	$165.55	3.762%	$171.778	$171.78	$171.80	$171.80
7 purchase totals =	$1,165.11		$1,254.8880	$1,254.88	$1,254.90	$1,254.90