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	$55.31	3.157%	$57.0561	$57.06	$57.05	$57.10
Purchase #2	$154.87	4.488%	$161.8206	$161.82	$161.80	$161.80
Purchase #3	$165.54	7.294%	$177.6145	$177.61	$177.60	$177.60
Purchase #4	$223.72	11.373%	$249.1637	$249.16	$249.15	$249.20
Purchase #5	$40.39	3.720%	$41.8925	$41.89	$41.90	$41.90
Purchase #6	$222.71	7.258%	$238.8743	$238.87	$238.85	$238.90
Purchase #7	$221.25	9.303%	$241.8329	$241.83	$241.85	$241.80
7 purchase totals =	$1,083.79		$1,168.2546	$1,168.24	$1,168.20	$1,168.30