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	$44.73	4.512%	$46.7482	$46.75	$46.75	$46.70
Purchase #2	$123.76	6.843%	$132.2289	$132.23	$132.25	$132.20
Purchase #3	$246.95	10.503%	$272.8872	$272.89	$272.90	$272.90
Purchase #4	$98.52	5.809%	$104.243	$104.24	$104.25	$104.20
Purchase #5	$140.88	7.127%	$150.9205	$150.92	$150.90	$150.90
Purchase #6	$140.57	11.575%	$156.841	$156.84	$156.85	$156.80
Purchase #7	$111.35	4.666%	$116.5456	$116.55	$116.55	$116.50
7 purchase totals =	$906.76		$980.4144	$980.42	$980.45	$980.20