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	$67.63	12.547%	$76.1155	$76.12	$76.10	$76.10
Purchase #2	$57.86	3.482%	$59.8747	$59.87	$59.85	$59.90
Purchase #3	$202.90	10.632%	$224.4723	$224.47	$224.45	$224.50
Purchase #4	$59.82	11.670%	$66.801	$66.80	$66.80	$66.80
Purchase #5	$200.28	5.596%	$211.4877	$211.49	$211.50	$211.50
Purchase #6	$21.82	13.854%	$24.8429	$24.84	$24.85	$24.80
Purchase #7	$178.56	5.432%	$188.2594	$188.26	$188.25	$188.30
7 purchase totals =	$788.87		$851.8535	$851.85	$851.80	$851.90