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	$47.85	12.382%	$53.7748	$53.77	$53.75	$53.80
Purchase #2	$37.73	3.633%	$39.1007	$39.10	$39.10	$39.10
Purchase #3	$51.86	3.234%	$53.5372	$53.54	$53.55	$53.50
Purchase #4	$83.29	13.502%	$94.5358	$94.54	$94.55	$94.50
Purchase #5	$124.53	8.721%	$135.3903	$135.39	$135.40	$135.40
Purchase #6	$185.56	10.565%	$205.1644	$205.16	$205.15	$205.20
Purchase #7	$95.45	10.615%	$105.582	$105.58	$105.60	$105.60
7 purchase totals =	$626.27		$687.0852	$687.08	$687.10	$687.10