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	$91.55	13.419%	$103.8351	$103.84	$103.85	$103.80
Purchase #2	$221.71	8.712%	$241.0254	$241.03	$241.05	$241.00
Purchase #3	$62.51	13.796%	$71.1339	$71.13	$71.15	$71.10
Purchase #4	$134.53	8.771%	$146.3296	$146.33	$146.35	$146.30
Purchase #5	$139.98	13.805%	$159.3042	$159.30	$159.30	$159.30
Purchase #6	$149.89	12.650%	$168.8511	$168.85	$168.85	$168.90
Purchase #7	$110.30	3.203%	$113.8329	$113.83	$113.85	$113.80
7 purchase totals =	$910.47		$1,004.3122	$1,004.31	$1,004.40	$1,004.20