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	$57.90	11.329%	$64.4595	$64.46	$64.45	$64.50
Purchase #2	$97.58	7.481%	$104.88	$104.88	$104.90	$104.90
Purchase #3	$26.89	3.805%	$27.9132	$27.91	$27.90	$27.90
Purchase #4	$104.40	6.765%	$111.4627	$111.46	$111.45	$111.50
Purchase #5	$201.80	5.257%	$212.4086	$212.41	$212.40	$212.40
Purchase #6	$220.68	12.492%	$248.2473	$248.25	$248.25	$248.20
Purchase #7	$109.51	8.309%	$118.6092	$118.61	$118.60	$118.60
7 purchase totals =	$818.76		$887.9805	$887.98	$887.95	$888.00