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	$134.46	12.170%	$150.8238	$150.82	$150.80	$150.80
Purchase #2	$207.64	7.353%	$222.9078	$222.91	$222.90	$222.90
Purchase #3	$14.39	11.416%	$16.0328	$16.03	$16.05	$16.00
Purchase #4	$181.82	6.613%	$193.8438	$193.84	$193.85	$193.80
Purchase #5	$162.41	3.140%	$167.5097	$167.51	$167.50	$167.50
Purchase #6	$222.31	7.219%	$238.3586	$238.36	$238.35	$238.40
Purchase #7	$46.81	12.220%	$52.5302	$52.53	$52.55	$52.50
7 purchase totals =	$969.84		$1,042.0067	$1,042.00	$1,042.00	$1,041.90