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	$86.49	10.423%	$95.5049	$95.50	$95.50	$95.50
Purchase #2	$95.81	4.667%	$100.2815	$100.28	$100.30	$100.30
Purchase #3	$30.59	8.503%	$33.1911	$33.19	$33.20	$33.20
Purchase #4	$148.63	11.600%	$165.8711	$165.87	$165.85	$165.90
Purchase #5	$219.76	7.759%	$236.8112	$236.81	$236.80	$236.80
Purchase #6	$172.88	3.718%	$179.3077	$179.31	$179.30	$179.30
Purchase #7	$28.65	13.394%	$32.4874	$32.49	$32.50	$32.50
7 purchase totals =	$782.81		$843.4549	$843.45	$843.45	$843.50