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	$162.77	3.283%	$168.1137	$168.11	$168.10	$168.10
Purchase #2	$95.31	10.248%	$105.0774	$105.08	$105.10	$105.10
Purchase #3	$229.79	12.123%	$257.6474	$257.65	$257.65	$257.60
Purchase #4	$62.73	11.216%	$69.7658	$69.77	$69.75	$69.80
Purchase #5	$58.33	11.132%	$64.8233	$64.82	$64.80	$64.80
Purchase #6	$95.64	13.826%	$108.8632	$108.86	$108.85	$108.90
Purchase #7	$9.32	11.199%	$10.3637	$10.36	$10.35	$10.40
7 purchase totals =	$713.89		$784.6545	$784.65	$784.60	$784.70