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	$186.95	7.161%	$200.3375	$200.34	$200.35	$200.30
Purchase #2	$115.89	9.787%	$127.2322	$127.23	$127.25	$127.20
Purchase #3	$188.50	8.704%	$204.907	$204.91	$204.90	$204.90
Purchase #4	$225.65	3.504%	$233.5568	$233.56	$233.55	$233.60
Purchase #5	$60.33	13.247%	$68.3219	$68.32	$68.30	$68.30
Purchase #6	$243.57	11.706%	$272.0823	$272.08	$272.10	$272.10
Purchase #7	$35.63	4.249%	$37.1439	$37.14	$37.15	$37.10
7 purchase totals =	$1,056.52		$1,143.5816	$1,143.58	$1,143.60	$1,143.50