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	$83.94	13.499%	$95.2711	$95.27	$95.25	$95.30
Purchase #2	$118.35	4.300%	$123.4391	$123.44	$123.45	$123.40
Purchase #3	$82.74	9.558%	$90.6483	$90.65	$90.65	$90.60
Purchase #4	$206.25	4.441%	$215.4096	$215.41	$215.40	$215.40
Purchase #5	$114.95	11.474%	$128.1394	$128.14	$128.15	$128.10
Purchase #6	$106.67	11.526%	$118.9648	$118.96	$118.95	$119.00
Purchase #7	$196.43	6.240%	$208.6872	$208.69	$208.70	$208.70
7 purchase totals =	$909.33		$980.5595	$980.56	$980.55	$980.50