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	$198.90	12.253%	$223.2712	$223.27	$223.25	$223.30
Purchase #2	$134.62	13.572%	$152.8906	$152.89	$152.90	$152.90
Purchase #3	$99.63	5.814%	$105.4225	$105.42	$105.40	$105.40
Purchase #4	$69.71	12.765%	$78.6085	$78.61	$78.60	$78.60
Purchase #5	$208.37	3.643%	$215.9609	$215.96	$215.95	$216.00
Purchase #6	$113.92	13.414%	$129.2012	$129.20	$129.20	$129.20
Purchase #7	$166.89	6.113%	$177.092	$177.09	$177.10	$177.10
7 purchase totals =	$992.04		$1,082.4469	$1,082.44	$1,082.40	$1,082.50