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	$127.88	7.385%	$137.3239	$137.32	$137.30	$137.30
Purchase #2	$220.35	5.860%	$233.2625	$233.26	$233.25	$233.30
Purchase #3	$160.97	4.490%	$168.1976	$168.20	$168.20	$168.20
Purchase #4	$190.52	3.368%	$196.9367	$196.94	$196.95	$196.90
Purchase #5	$190.88	9.743%	$209.4774	$209.48	$209.50	$209.50
Purchase #6	$63.62	9.109%	$69.4151	$69.42	$69.40	$69.40
Purchase #7	$132.57	13.805%	$150.8713	$150.87	$150.85	$150.90
7 purchase totals =	$1,086.79		$1,165.4845	$1,165.49	$1,165.45	$1,165.50