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	$94.87	6.586%	$101.1181	$101.12	$101.10	$101.10
Purchase #2	$245.45	5.329%	$258.53	$258.53	$258.55	$258.50
Purchase #3	$86.41	8.454%	$93.7151	$93.72	$93.70	$93.70
Purchase #4	$210.43	13.106%	$238.009	$238.01	$238.00	$238.00
Purchase #5	$67.31	7.105%	$72.0924	$72.09	$72.10	$72.10
Purchase #6	$24.46	4.233%	$25.4954	$25.50	$25.50	$25.50
Purchase #7	$111.91	10.603%	$123.7758	$123.78	$123.80	$123.80
7 purchase totals =	$840.84		$912.7358	$912.75	$912.75	$912.70