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	$189.93	10.774%	$210.3931	$210.39	$210.40	$210.40
Purchase #2	$13.77	12.141%	$15.4418	$15.44	$15.45	$15.40
Purchase #3	$78.31	5.360%	$82.5074	$82.51	$82.50	$82.50
Purchase #4	$178.55	4.325%	$186.2723	$186.27	$186.25	$186.30
Purchase #5	$57.72	9.426%	$63.1607	$63.16	$63.15	$63.20
Purchase #6	$62.69	11.431%	$69.8561	$69.86	$69.85	$69.90
Purchase #7	$75.97	12.773%	$85.6736	$85.67	$85.65	$85.70
7 purchase totals =	$656.94		$713.3050	$713.30	$713.25	$713.40