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	$57.48	13.495%	$65.2369	$65.24	$65.25	$65.20
Purchase #2	$176.84	12.792%	$199.4614	$199.46	$199.45	$199.50
Purchase #3	$226.91	3.673%	$235.2444	$235.24	$235.25	$235.20
Purchase #4	$131.56	10.220%	$145.0054	$145.01	$145.00	$145.00
Purchase #5	$89.88	10.772%	$99.5619	$99.56	$99.55	$99.60
Purchase #6	$228.47	4.592%	$238.9613	$238.96	$238.95	$239.00
Purchase #7	$217.56	3.836%	$225.9056	$225.91	$225.90	$225.90
7 purchase totals =	$1,128.70		$1,209.3769	$1,209.38	$1,209.35	$1,209.40