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	$68.94	13.702%	$78.3862	$78.39	$78.40	$78.40
Purchase #2	$146.33	4.562%	$153.0056	$153.01	$153.00	$153.00
Purchase #3	$232.89	4.460%	$243.2769	$243.28	$243.30	$243.30
Purchase #4	$234.37	4.102%	$243.9839	$243.98	$244.00	$244.00
Purchase #5	$30.78	5.866%	$32.5856	$32.59	$32.60	$32.60
Purchase #6	$116.63	13.787%	$132.7098	$132.71	$132.70	$132.70
Purchase #7	$183.57	4.249%	$191.3699	$191.37	$191.35	$191.40
7 purchase totals =	$1,013.51		$1,075.3179	$1,075.33	$1,075.35	$1,075.40