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	$144.34	8.176%	$156.1412	$156.14	$156.15	$156.10
Purchase #2	$114.53	11.585%	$127.7983	$127.80	$127.80	$127.80
Purchase #3	$5.85	6.492%	$6.2298	$6.23	$6.25	$6.20
Purchase #4	$91.29	13.161%	$103.3047	$103.30	$103.30	$103.30
Purchase #5	$190.36	4.815%	$199.5258	$199.53	$199.55	$199.50
Purchase #6	$153.68	9.164%	$167.7632	$167.76	$167.75	$167.80
Purchase #7	$239.41	12.555%	$269.4679	$269.47	$269.45	$269.50
7 purchase totals =	$939.46		$1,030.2309	$1,030.23	$1,030.25	$1,030.20