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	$146.88	4.237%	$153.1033	$153.10	$153.10	$153.10
Purchase #2	$73.54	11.490%	$81.9897	$81.99	$82.00	$82.00
Purchase #3	$238.93	7.159%	$256.035	$256.04	$256.05	$256.00
Purchase #4	$146.69	12.436%	$164.9324	$164.93	$164.95	$164.90
Purchase #5	$52.39	13.244%	$59.3285	$59.33	$59.35	$59.30
Purchase #6	$86.71	9.444%	$94.8989	$94.90	$94.90	$94.90
Purchase #7	$215.92	8.820%	$234.9641	$234.96	$234.95	$235.00
7 purchase totals =	$961.06		$1,045.2519	$1,045.25	$1,045.30	$1,045.20