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	$241.34	4.532%	$252.2775	$252.28	$252.30	$252.30
Purchase #2	$152.86	12.154%	$171.4386	$171.44	$171.45	$171.40
Purchase #3	$225.42	13.298%	$255.3964	$255.40	$255.40	$255.40
Purchase #4	$174.66	5.688%	$184.5947	$184.59	$184.60	$184.60
Purchase #5	$100.63	11.543%	$112.2457	$112.25	$112.25	$112.20
Purchase #6	$75.65	9.530%	$82.8594	$82.86	$82.85	$82.90
Purchase #7	$75.28	13.753%	$85.6333	$85.63	$85.65	$85.60
7 purchase totals =	$1,045.84		$1,144.4456	$1,144.45	$1,144.50	$1,144.40