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	$59.68	9.811%	$65.5352	$65.54	$65.55	$65.50
Purchase #2	$29.59	5.695%	$31.2752	$31.28	$31.30	$31.30
Purchase #3	$79.63	12.577%	$89.6451	$89.65	$89.65	$89.60
Purchase #4	$83.66	9.815%	$91.8712	$91.87	$91.85	$91.90
Purchase #5	$176.59	13.205%	$199.9087	$199.91	$199.90	$199.90
Purchase #6	$115.86	8.193%	$125.3524	$125.35	$125.35	$125.40
Purchase #7	$135.93	11.286%	$151.2711	$151.27	$151.25	$151.30
7 purchase totals =	$680.94		$754.8589	$754.87	$754.85	$754.90