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	$137.39	3.526%	$142.2344	$142.23	$142.25	$142.20
Purchase #2	$99.89	11.191%	$111.0687	$111.07	$111.05	$111.10
Purchase #3	$27.94	11.551%	$31.1673	$31.17	$31.15	$31.20
Purchase #4	$234.90	13.730%	$267.1518	$267.15	$267.15	$267.20
Purchase #5	$47.37	4.204%	$49.3614	$49.36	$49.35	$49.40
Purchase #6	$112.88	11.515%	$125.8781	$125.88	$125.90	$125.90
Purchase #7	$202.57	4.151%	$210.9787	$210.98	$211.00	$211.00
7 purchase totals =	$862.94		$937.8404	$937.84	$937.85	$938.00