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	$218.81	13.160%	$247.6054	$247.61	$247.60	$247.60
Purchase #2	$156.95	6.761%	$167.5614	$167.56	$167.55	$167.60
Purchase #3	$176.61	6.459%	$188.0172	$188.02	$188.00	$188.00
Purchase #4	$85.37	9.382%	$93.3794	$93.38	$93.40	$93.40
Purchase #5	$171.67	4.528%	$179.4432	$179.44	$179.45	$179.40
Purchase #6	$95.44	7.157%	$102.2706	$102.27	$102.25	$102.30
Purchase #7	$80.36	11.461%	$89.5701	$89.57	$89.55	$89.60
7 purchase totals =	$985.21		$1,067.8473	$1,067.85	$1,067.80	$1,067.90