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	$218.54	11.810%	$244.3496	$244.35	$244.35	$244.30
Purchase #2	$134.50	8.423%	$145.8289	$145.83	$145.85	$145.80
Purchase #3	$175.29	13.459%	$198.8823	$198.88	$198.90	$198.90
Purchase #4	$30.70	10.386%	$33.8885	$33.89	$33.90	$33.90
Purchase #5	$179.83	10.543%	$198.7895	$198.79	$198.80	$198.80
Purchase #6	$167.37	13.143%	$189.3674	$189.37	$189.35	$189.40
Purchase #7	$182.54	3.618%	$189.1443	$189.14	$189.15	$189.10
7 purchase totals =	$1,088.77		$1,200.2505	$1,200.25	$1,200.30	$1,200.20