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	$43.82	13.718%	$49.8312	$49.83	$49.85	$49.80
Purchase #2	$156.37	5.774%	$165.3988	$165.40	$165.40	$165.40
Purchase #3	$18.42	4.683%	$19.2826	$19.28	$19.30	$19.30
Purchase #4	$240.65	11.754%	$268.936	$268.94	$268.95	$268.90
Purchase #5	$232.64	11.620%	$259.6728	$259.67	$259.65	$259.70
Purchase #6	$73.75	6.842%	$78.796	$78.80	$78.80	$78.80
Purchase #7	$65.79	10.244%	$72.5295	$72.53	$72.55	$72.50
7 purchase totals =	$831.44		$914.4469	$914.45	$914.50	$914.40