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	$107.61	4.355%	$112.2964	$112.30	$112.30	$112.30
Purchase #2	$200.30	6.640%	$213.5999	$213.60	$213.60	$213.60
Purchase #3	$98.62	12.378%	$110.8272	$110.83	$110.85	$110.80
Purchase #4	$77.86	10.497%	$86.033	$86.03	$86.05	$86.00
Purchase #5	$85.79	5.573%	$90.5711	$90.57	$90.55	$90.60
Purchase #6	$190.74	5.136%	$200.5364	$200.54	$200.55	$200.50
Purchase #7	$119.30	3.498%	$123.4731	$123.47	$123.45	$123.50
7 purchase totals =	$880.22		$937.3371	$937.34	$937.35	$937.30