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	$93.78	3.354%	$96.9254	$96.93	$96.95	$96.90
Purchase #2	$102.94	8.717%	$111.9133	$111.91	$111.90	$111.90
Purchase #3	$173.49	9.213%	$189.4736	$189.47	$189.45	$189.50
Purchase #4	$127.62	13.289%	$144.5794	$144.58	$144.60	$144.60
Purchase #5	$234.59	11.599%	$261.8001	$261.80	$261.80	$261.80
Purchase #6	$74.55	4.745%	$78.0874	$78.09	$78.10	$78.10
Purchase #7	$195.82	13.664%	$222.5768	$222.58	$222.60	$222.60
7 purchase totals =	$1,002.79		$1,105.3560	$1,105.36	$1,105.40	$1,105.40