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	$63.40	13.732%	$72.1061	$72.11	$72.10	$72.10
Purchase #2	$97.97	9.585%	$107.3604	$107.36	$107.35	$107.40
Purchase #3	$44.61	11.193%	$49.6032	$49.60	$49.60	$49.60
Purchase #4	$185.30	8.328%	$200.7318	$200.73	$200.75	$200.70
Purchase #5	$65.99	9.289%	$72.1198	$72.12	$72.10	$72.10
Purchase #6	$101.96	12.248%	$114.4481	$114.45	$114.45	$114.40
Purchase #7	$189.65	13.836%	$215.89	$215.89	$215.90	$215.90
7 purchase totals =	$748.88		$832.2594	$832.26	$832.25	$832.20