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	$72.57	5.202%	$76.3451	$76.35	$76.35	$76.30
Purchase #2	$137.68	3.851%	$142.9821	$142.98	$143.00	$143.00
Purchase #3	$10.72	9.697%	$11.7595	$11.76	$11.75	$11.80
Purchase #4	$67.60	12.239%	$75.8736	$75.87	$75.85	$75.90
Purchase #5	$55.29	7.780%	$59.5916	$59.59	$59.60	$59.60
Purchase #6	$58.90	10.841%	$65.2853	$65.29	$65.30	$65.30
Purchase #7	$170.59	8.510%	$185.1072	$185.11	$185.10	$185.10
7 purchase totals =	$573.35		$616.9444	$616.95	$616.95	$617.00