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	$86.92	13.686%	$98.8159	$98.82	$98.80	$98.80
Purchase #2	$16.97	13.710%	$19.2966	$19.30	$19.30	$19.30
Purchase #3	$141.90	7.222%	$152.148	$152.15	$152.15	$152.10
Purchase #4	$84.57	10.680%	$93.6021	$93.60	$93.60	$93.60
Purchase #5	$136.98	9.751%	$150.3369	$150.34	$150.35	$150.30
Purchase #6	$94.71	5.566%	$99.9816	$99.98	$100.00	$100.00
Purchase #7	$148.59	9.354%	$162.4891	$162.49	$162.50	$162.50
7 purchase totals =	$710.64		$776.6702	$776.68	$776.70	$776.60