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	$87.29	12.772%	$98.4387	$98.44	$98.45	$98.40
Purchase #2	$178.39	7.768%	$192.2473	$192.25	$192.25	$192.20
Purchase #3	$36.80	5.536%	$38.8372	$38.84	$38.85	$38.80
Purchase #4	$26.87	5.857%	$28.4438	$28.44	$28.45	$28.40
Purchase #5	$17.74	13.164%	$20.0753	$20.08	$20.10	$20.10
Purchase #6	$55.48	6.741%	$59.2199	$59.22	$59.20	$59.20
Purchase #7	$98.80	5.156%	$103.8941	$103.89	$103.90	$103.90
7 purchase totals =	$501.37		$541.1563	$541.16	$541.20	$541.00