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	$197.33	13.402%	$223.7762	$223.78	$223.80	$223.80
Purchase #2	$67.57	10.628%	$74.7513	$74.75	$74.75	$74.80
Purchase #3	$103.43	5.840%	$109.4703	$109.47	$109.45	$109.50
Purchase #4	$94.39	11.857%	$105.5818	$105.58	$105.60	$105.60
Purchase #5	$181.44	13.745%	$206.3789	$206.38	$206.40	$206.40
Purchase #6	$50.61	5.112%	$53.1972	$53.20	$53.20	$53.20
Purchase #7	$221.33	5.776%	$234.114	$234.11	$234.10	$234.10
7 purchase totals =	$916.10		$1,007.2697	$1,007.27	$1,007.30	$1,007.40