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	$29.80	8.208%	$32.246	$32.25	$32.25	$32.20
Purchase #2	$69.85	12.490%	$78.5743	$78.57	$78.55	$78.60
Purchase #3	$90.72	7.567%	$97.5848	$97.58	$97.60	$97.60
Purchase #4	$12.53	12.411%	$14.0851	$14.09	$14.10	$14.10
Purchase #5	$248.79	13.350%	$282.0035	$282.00	$282.00	$282.00
Purchase #6	$240.82	12.216%	$270.2386	$270.24	$270.25	$270.20
Purchase #7	$210.82	13.305%	$238.8696	$238.87	$238.85	$238.90
7 purchase totals =	$903.33		$1,013.6019	$1,013.60	$1,013.60	$1,013.60