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	$52.30	8.653%	$56.8255	$56.83	$56.85	$56.80
Purchase #2	$57.25	5.609%	$60.4612	$60.46	$60.45	$60.50
Purchase #3	$60.98	7.745%	$65.7029	$65.70	$65.70	$65.70
Purchase #4	$46.67	12.191%	$52.3595	$52.36	$52.35	$52.40
Purchase #5	$163.56	7.157%	$175.266	$175.27	$175.25	$175.30
Purchase #6	$228.26	12.370%	$256.4958	$256.50	$256.50	$256.50
Purchase #7	$108.69	11.229%	$120.8948	$120.89	$120.90	$120.90
7 purchase totals =	$717.71		$788.0057	$788.01	$788.00	$788.10