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	$152.94	5.107%	$160.7506	$160.75	$160.75	$160.80
Purchase #2	$6.35	8.424%	$6.8849	$6.88	$6.90	$6.90
Purchase #3	$226.52	3.758%	$235.0326	$235.03	$235.05	$235.00
Purchase #4	$95.90	3.186%	$98.9554	$98.96	$98.95	$99.00
Purchase #5	$152.51	4.110%	$158.7782	$158.78	$158.80	$158.80
Purchase #6	$236.66	11.415%	$263.6747	$263.67	$263.65	$263.70
Purchase #7	$70.42	12.109%	$78.9472	$78.95	$78.95	$78.90
7 purchase totals =	$941.30		$1,003.0236	$1,003.02	$1,003.05	$1,003.10