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	$211.42	12.619%	$238.0991	$238.10	$238.10	$238.10
Purchase #2	$210.34	4.376%	$219.5445	$219.54	$219.55	$219.50
Purchase #3	$81.79	6.231%	$86.8863	$86.89	$86.90	$86.90
Purchase #4	$204.59	9.168%	$223.3468	$223.35	$223.35	$223.30
Purchase #5	$94.98	5.718%	$100.411	$100.41	$100.40	$100.40
Purchase #6	$217.25	11.872%	$243.0419	$243.04	$243.05	$243.00
Purchase #7	$25.78	5.787%	$27.2719	$27.27	$27.25	$27.30
7 purchase totals =	$1,046.15		$1,138.6015	$1,138.60	$1,138.60	$1,138.50