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	$100.52	7.123%	$107.68	$107.68	$107.70	$107.70
Purchase #2	$172.88	13.724%	$196.6061	$196.61	$196.60	$196.60
Purchase #3	$72.52	3.149%	$74.8037	$74.80	$74.80	$74.80
Purchase #4	$78.41	5.380%	$82.6285	$82.63	$82.65	$82.60
Purchase #5	$189.85	3.597%	$196.6789	$196.68	$196.70	$196.70
Purchase #6	$216.64	13.481%	$245.8452	$245.85	$245.85	$245.80
Purchase #7	$181.62	5.645%	$191.8724	$191.87	$191.85	$191.90
7 purchase totals =	$1,012.44		$1,096.1148	$1,096.12	$1,096.15	$1,096.10