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	$174.71	10.237%	$192.5951	$192.60	$192.60	$192.60
Purchase #2	$59.56	6.414%	$63.3802	$63.38	$63.40	$63.40
Purchase #3	$95.77	3.332%	$98.9611	$98.96	$98.95	$99.00
Purchase #4	$9.94	4.568%	$10.3941	$10.39	$10.40	$10.40
Purchase #5	$100.48	10.734%	$111.2655	$111.27	$111.25	$111.30
Purchase #6	$74.90	13.533%	$85.0362	$85.04	$85.05	$85.00
Purchase #7	$153.66	9.488%	$168.2393	$168.24	$168.25	$168.20
7 purchase totals =	$669.02		$729.8715	$729.88	$729.90	$729.90