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	$122.76	6.400%	$130.6166	$130.62	$130.60	$130.60
Purchase #2	$42.65	7.542%	$45.8667	$45.87	$45.85	$45.90
Purchase #3	$137.97	6.220%	$146.5517	$146.55	$146.55	$146.60
Purchase #4	$163.98	13.835%	$186.6666	$186.67	$186.65	$186.70
Purchase #5	$50.61	8.646%	$54.9857	$54.99	$55.00	$55.00
Purchase #6	$81.91	4.522%	$85.614	$85.61	$85.60	$85.60
Purchase #7	$69.95	3.766%	$72.5843	$72.58	$72.60	$72.60
7 purchase totals =	$669.83		$722.8856	$722.89	$722.85	$723.00