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	$153.55	9.690%	$168.429	$168.43	$168.45	$168.40
Purchase #2	$215.90	11.586%	$240.9142	$240.91	$240.90	$240.90
Purchase #3	$195.59	7.205%	$209.6823	$209.68	$209.70	$209.70
Purchase #4	$79.74	8.390%	$86.4302	$86.43	$86.45	$86.40
Purchase #5	$88.68	11.643%	$99.005	$99.01	$99.00	$99.00
Purchase #6	$180.84	13.691%	$205.5988	$205.60	$205.60	$205.60
Purchase #7	$82.72	6.645%	$88.2167	$88.22	$88.20	$88.20
7 purchase totals =	$997.02		$1,098.2762	$1,098.28	$1,098.30	$1,098.20