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	$238.26	7.582%	$256.3249	$256.32	$256.30	$256.30
Purchase #2	$130.31	8.564%	$141.4697	$141.47	$141.45	$141.50
Purchase #3	$201.66	6.506%	$214.78	$214.78	$214.80	$214.80
Purchase #4	$173.88	10.661%	$192.4173	$192.42	$192.40	$192.40
Purchase #5	$189.70	10.453%	$209.5293	$209.53	$209.55	$209.50
Purchase #6	$84.49	6.764%	$90.2049	$90.20	$90.20	$90.20
Purchase #7	$66.72	10.787%	$73.9171	$73.92	$73.90	$73.90
7 purchase totals =	$1,085.02		$1,178.6432	$1,178.64	$1,178.60	$1,178.60