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	$96.93	13.200%	$109.7248	$109.72	$109.70	$109.70
Purchase #2	$228.40	6.372%	$242.9536	$242.95	$242.95	$243.00
Purchase #3	$45.76	9.634%	$50.1685	$50.17	$50.15	$50.20
Purchase #4	$103.73	8.447%	$112.4921	$112.49	$112.50	$112.50
Purchase #5	$182.28	13.537%	$206.9552	$206.96	$206.95	$207.00
Purchase #6	$152.59	7.134%	$163.4758	$163.48	$163.50	$163.50
Purchase #7	$57.25	4.122%	$59.6098	$59.61	$59.60	$59.60
7 purchase totals =	$866.94		$945.3798	$945.38	$945.35	$945.50