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	$85.98	12.556%	$96.7756	$96.78	$96.80	$96.80
Purchase #2	$17.55	13.390%	$19.8999	$19.90	$19.90	$19.90
Purchase #3	$50.26	6.219%	$53.3857	$53.39	$53.40	$53.40
Purchase #4	$86.85	4.581%	$90.8286	$90.83	$90.85	$90.80
Purchase #5	$52.50	6.271%	$55.7923	$55.79	$55.80	$55.80
Purchase #6	$204.53	11.217%	$227.4721	$227.47	$227.45	$227.50
Purchase #7	$193.43	12.745%	$218.0827	$218.08	$218.10	$218.10
7 purchase totals =	$691.10		$762.2369	$762.24	$762.30	$762.30