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	$111.48	12.141%	$125.0148	$125.01	$125.00	$125.00
Purchase #2	$142.45	6.192%	$151.2705	$151.27	$151.25	$151.30
Purchase #3	$54.25	13.104%	$61.3589	$61.36	$61.35	$61.40
Purchase #4	$167.43	11.116%	$186.0415	$186.04	$186.05	$186.00
Purchase #5	$84.58	6.755%	$90.2934	$90.29	$90.30	$90.30
Purchase #6	$120.73	10.396%	$133.2811	$133.28	$133.30	$133.30
Purchase #7	$199.42	4.430%	$208.2543	$208.25	$208.25	$208.30
7 purchase totals =	$880.34		$955.5145	$955.50	$955.50	$955.60