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	$187.79	7.676%	$202.2048	$202.20	$202.20	$202.20
Purchase #2	$233.91	9.269%	$255.5911	$255.59	$255.60	$255.60
Purchase #3	$37.87	7.818%	$40.8307	$40.83	$40.85	$40.80
Purchase #4	$10.73	12.847%	$12.1085	$12.11	$12.10	$12.10
Purchase #5	$43.65	9.432%	$47.7671	$47.77	$47.75	$47.80
Purchase #6	$49.30	8.491%	$53.4861	$53.49	$53.50	$53.50
Purchase #7	$99.32	12.517%	$111.7519	$111.75	$111.75	$111.80
7 purchase totals =	$662.57		$723.7402	$723.74	$723.75	$723.80