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	$148.41	5.724%	$156.905	$156.91	$156.90	$156.90
Purchase #2	$98.96	12.435%	$111.2657	$111.27	$111.25	$111.30
Purchase #3	$128.77	4.608%	$134.7037	$134.70	$134.70	$134.70
Purchase #4	$117.56	4.345%	$122.668	$122.67	$122.65	$122.70
Purchase #5	$63.73	12.325%	$71.5847	$71.58	$71.60	$71.60
Purchase #6	$122.40	4.577%	$128.0022	$128.00	$128.00	$128.00
Purchase #7	$99.41	4.310%	$103.6946	$103.69	$103.70	$103.70
7 purchase totals =	$779.24		$828.8239	$828.82	$828.80	$828.90