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	$185.95	7.641%	$200.1584	$200.16	$200.15	$200.20
Purchase #2	$231.61	10.128%	$255.0675	$255.07	$255.05	$255.10
Purchase #3	$7.46	10.235%	$8.2235	$8.22	$8.20	$8.20
Purchase #4	$42.56	4.712%	$44.5654	$44.57	$44.55	$44.60
Purchase #5	$152.33	7.678%	$164.0259	$164.03	$164.05	$164.00
Purchase #6	$59.93	11.518%	$66.8327	$66.83	$66.85	$66.80
Purchase #7	$44.38	3.773%	$46.0545	$46.05	$46.05	$46.10
7 purchase totals =	$724.22		$784.9279	$784.93	$784.90	$785.00