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	$31.56	3.727%	$32.7362	$32.74	$32.75	$32.70
Purchase #2	$100.89	4.246%	$105.1738	$105.17	$105.15	$105.20
Purchase #3	$58.74	5.121%	$61.7481	$61.75	$61.75	$61.70
Purchase #4	$141.90	7.790%	$152.954	$152.95	$152.95	$153.00
Purchase #5	$62.83	6.831%	$67.1219	$67.12	$67.10	$67.10
Purchase #6	$181.90	9.725%	$199.5898	$199.59	$199.60	$199.60
Purchase #7	$61.86	6.578%	$65.9292	$65.93	$65.95	$65.90
7 purchase totals =	$639.68		$685.2530	$685.25	$685.25	$685.20