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	$139.58	13.835%	$158.8909	$158.89	$158.90	$158.90
Purchase #2	$220.80	6.808%	$235.8321	$235.83	$235.85	$235.80
Purchase #3	$97.98	12.581%	$110.3069	$110.31	$110.30	$110.30
Purchase #4	$119.47	10.185%	$131.638	$131.64	$131.65	$131.60
Purchase #5	$87.69	9.616%	$96.1223	$96.12	$96.10	$96.10
Purchase #6	$212.88	9.822%	$233.7891	$233.79	$233.80	$233.80
Purchase #7	$118.77	5.250%	$125.0054	$125.01	$125.00	$125.00
7 purchase totals =	$997.17		$1,091.5847	$1,091.59	$1,091.60	$1,091.50