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	$88.56	10.707%	$98.0421	$98.04	$98.05	$98.00
Purchase #2	$17.32	7.440%	$18.6086	$18.61	$18.60	$18.60
Purchase #3	$49.78	6.719%	$53.1247	$53.12	$53.10	$53.10
Purchase #4	$104.53	5.115%	$109.8767	$109.88	$109.90	$109.90
Purchase #5	$231.81	10.310%	$255.7096	$255.71	$255.70	$255.70
Purchase #6	$74.59	4.534%	$77.9719	$77.97	$77.95	$78.00
Purchase #7	$29.34	5.384%	$30.9197	$30.92	$30.90	$30.90
7 purchase totals =	$595.93		$644.2533	$644.25	$644.20	$644.20