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	$248.27	7.165%	$266.0585	$266.06	$266.05	$266.10
Purchase #2	$184.77	7.173%	$198.0236	$198.02	$198.00	$198.00
Purchase #3	$86.32	13.693%	$98.1398	$98.14	$98.15	$98.10
Purchase #4	$138.85	9.858%	$152.5378	$152.54	$152.55	$152.50
Purchase #5	$139.75	11.274%	$155.5054	$155.51	$155.50	$155.50
Purchase #6	$31.39	12.685%	$35.3718	$35.37	$35.35	$35.40
Purchase #7	$157.65	4.435%	$164.6418	$164.64	$164.65	$164.60
7 purchase totals =	$987.00		$1,070.2787	$1,070.28	$1,070.25	$1,070.20