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	$73.68	7.542%	$79.2369	$79.24	$79.25	$79.20
Purchase #2	$161.70	4.407%	$168.8261	$168.83	$168.85	$168.80
Purchase #3	$58.50	7.481%	$62.8764	$62.88	$62.90	$62.90
Purchase #4	$39.33	8.391%	$42.6302	$42.63	$42.65	$42.60
Purchase #5	$175.90	9.305%	$192.2675	$192.27	$192.25	$192.30
Purchase #6	$48.44	4.477%	$50.6087	$50.61	$50.60	$50.60
Purchase #7	$121.72	10.810%	$134.8779	$134.88	$134.90	$134.90
7 purchase totals =	$679.27		$731.3237	$731.34	$731.40	$731.30