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	$47.65	12.616%	$53.6615	$53.66	$53.65	$53.70
Purchase #2	$26.37	7.105%	$28.2436	$28.24	$28.25	$28.20
Purchase #3	$158.91	6.607%	$169.4092	$169.41	$169.40	$169.40
Purchase #4	$187.67	4.757%	$196.5975	$196.60	$196.60	$196.60
Purchase #5	$48.76	5.152%	$51.2721	$51.27	$51.25	$51.30
Purchase #6	$57.40	13.508%	$65.1536	$65.15	$65.15	$65.20
Purchase #7	$75.45	13.497%	$85.6335	$85.63	$85.65	$85.60
7 purchase totals =	$602.21		$649.9710	$649.96	$649.95	$650.00