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	$47.79	12.131%	$53.5874	$53.59	$53.60	$53.60
Purchase #2	$7.66	5.399%	$8.0736	$8.07	$8.05	$8.10
Purchase #3	$195.30	10.620%	$216.0409	$216.04	$216.05	$216.00
Purchase #4	$170.25	9.724%	$186.8051	$186.81	$186.80	$186.80
Purchase #5	$151.75	6.812%	$162.0872	$162.09	$162.10	$162.10
Purchase #6	$244.41	11.526%	$272.5807	$272.58	$272.60	$272.60
Purchase #7	$98.62	13.343%	$111.7789	$111.78	$111.80	$111.80
7 purchase totals =	$915.78		$1,010.9538	$1,010.96	$1,011.00	$1,011.00