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	$220.40	13.254%	$249.6118	$249.61	$249.60	$249.60
Purchase #2	$211.81	6.404%	$225.3743	$225.37	$225.35	$225.40
Purchase #3	$90.39	6.623%	$96.3765	$96.38	$96.40	$96.40
Purchase #4	$98.37	7.648%	$105.8933	$105.89	$105.90	$105.90
Purchase #5	$7.32	3.313%	$7.5625	$7.56	$7.55	$7.60
Purchase #6	$12.90	12.745%	$14.5441	$14.54	$14.55	$14.50
Purchase #7	$191.99	12.703%	$216.3785	$216.38	$216.40	$216.40
7 purchase totals =	$833.18		$915.7410	$915.73	$915.75	$915.80