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	$143.74	6.207%	$152.6619	$152.66	$152.65	$152.70
Purchase #2	$162.47	8.380%	$176.085	$176.09	$176.10	$176.10
Purchase #3	$117.92	5.110%	$123.9457	$123.95	$123.95	$123.90
Purchase #4	$173.96	9.836%	$191.0707	$191.07	$191.05	$191.10
Purchase #5	$250.50	9.745%	$274.9112	$274.91	$274.90	$274.90
Purchase #6	$194.39	11.405%	$216.5602	$216.56	$216.55	$216.60
Purchase #7	$197.71	12.314%	$222.056	$222.06	$222.05	$222.10
7 purchase totals =	$1,240.69		$1,357.2907	$1,357.30	$1,357.25	$1,357.40