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	$152.88	13.340%	$173.2742	$173.27	$173.25	$173.30
Purchase #2	$40.98	13.443%	$46.4889	$46.49	$46.50	$46.50
Purchase #3	$52.60	7.489%	$56.5392	$56.54	$56.55	$56.50
Purchase #4	$25.37	10.430%	$28.0161	$28.02	$28.00	$28.00
Purchase #5	$48.74	6.344%	$51.8321	$51.83	$51.85	$51.80
Purchase #6	$169.89	6.155%	$180.3467	$180.35	$180.35	$180.30
Purchase #7	$146.27	4.584%	$152.975	$152.98	$153.00	$153.00
7 purchase totals =	$636.73		$689.4722	$689.48	$689.50	$689.40