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	$201.55	8.407%	$218.4943	$218.49	$218.50	$218.50
Purchase #2	$183.53	3.370%	$189.715	$189.72	$189.70	$189.70
Purchase #3	$22.87	4.328%	$23.8598	$23.86	$23.85	$23.90
Purchase #4	$136.47	7.181%	$146.2699	$146.27	$146.25	$146.30
Purchase #5	$160.77	7.532%	$172.8792	$172.88	$172.90	$172.90
Purchase #6	$165.65	4.166%	$172.551	$172.55	$172.55	$172.60
Purchase #7	$75.48	11.242%	$83.9655	$83.97	$83.95	$84.00
7 purchase totals =	$946.32		$1,007.7347	$1,007.74	$1,007.70	$1,007.90