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	$110.35	6.609%	$117.643	$117.64	$117.65	$117.60
Purchase #2	$108.56	4.529%	$113.4767	$113.48	$113.50	$113.50
Purchase #3	$150.55	11.441%	$167.7744	$167.77	$167.75	$167.80
Purchase #4	$222.52	9.512%	$243.6861	$243.69	$243.70	$243.70
Purchase #5	$101.34	8.443%	$109.8961	$109.90	$109.90	$109.90
Purchase #6	$234.83	3.588%	$243.2557	$243.26	$243.25	$243.30
Purchase #7	$63.58	12.619%	$71.6032	$71.60	$71.60	$71.60
7 purchase totals =	$991.73		$1,067.3352	$1,067.34	$1,067.35	$1,067.40