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	$179.74	3.140%	$185.3838	$185.38	$185.40	$185.40
Purchase #2	$192.50	4.375%	$200.9219	$200.92	$200.90	$200.90
Purchase #3	$152.71	6.256%	$162.2635	$162.26	$162.25	$162.30
Purchase #4	$167.75	11.182%	$186.5078	$186.51	$186.50	$186.50
Purchase #5	$71.76	10.673%	$79.4189	$79.42	$79.40	$79.40
Purchase #6	$101.83	10.474%	$112.4957	$112.50	$112.50	$112.50
Purchase #7	$143.35	13.448%	$162.6277	$162.63	$162.65	$162.60
7 purchase totals =	$1,009.64		$1,089.6193	$1,089.62	$1,089.60	$1,089.60