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	$237.67	7.234%	$254.863	$254.86	$254.85	$254.90
Purchase #2	$82.98	13.629%	$94.2893	$94.29	$94.30	$94.30
Purchase #3	$169.66	13.127%	$191.9313	$191.93	$191.95	$191.90
Purchase #4	$160.55	4.848%	$168.3335	$168.33	$168.35	$168.30
Purchase #5	$171.75	8.835%	$186.9241	$186.92	$186.90	$186.90
Purchase #6	$25.83	12.504%	$29.0598	$29.06	$29.05	$29.10
Purchase #7	$156.29	6.225%	$166.0191	$166.02	$166.00	$166.00
7 purchase totals =	$1,004.73		$1,091.4201	$1,091.41	$1,091.40	$1,091.40