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	$91.59	9.844%	$100.6061	$100.61	$100.60	$100.60
Purchase #2	$230.78	6.287%	$245.2891	$245.29	$245.30	$245.30
Purchase #3	$125.87	9.871%	$138.2946	$138.29	$138.30	$138.30
Purchase #4	$119.97	6.247%	$127.4645	$127.46	$127.45	$127.50
Purchase #5	$199.39	9.624%	$218.5793	$218.58	$218.60	$218.60
Purchase #6	$79.77	8.503%	$86.5528	$86.55	$86.55	$86.60
Purchase #7	$120.26	7.459%	$129.2302	$129.23	$129.25	$129.20
7 purchase totals =	$967.63		$1,046.0166	$1,046.01	$1,046.05	$1,046.10