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	$244.36	13.308%	$276.8794	$276.88	$276.90	$276.90
Purchase #2	$224.40	11.407%	$249.9973	$250.00	$250.00	$250.00
Purchase #3	$51.85	3.389%	$53.6072	$53.61	$53.60	$53.60
Purchase #4	$35.37	11.573%	$39.4634	$39.46	$39.45	$39.50
Purchase #5	$150.56	5.539%	$158.8995	$158.90	$158.90	$158.90
Purchase #6	$221.82	10.162%	$244.3613	$244.36	$244.35	$244.40
Purchase #7	$147.49	10.132%	$162.4337	$162.43	$162.45	$162.40
7 purchase totals =	$1,075.85		$1,185.6418	$1,185.64	$1,185.65	$1,185.70