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	$70.82	3.686%	$73.4304	$73.43	$73.45	$73.40
Purchase #2	$59.84	8.448%	$64.8953	$64.90	$64.90	$64.90
Purchase #3	$216.64	11.637%	$241.8504	$241.85	$241.85	$241.90
Purchase #4	$200.73	3.528%	$207.8118	$207.81	$207.80	$207.80
Purchase #5	$202.38	3.690%	$209.8478	$209.85	$209.85	$209.80
Purchase #6	$189.41	3.566%	$196.1644	$196.16	$196.15	$196.20
Purchase #7	$63.47	10.776%	$70.3095	$70.31	$70.30	$70.30
7 purchase totals =	$1,003.29		$1,064.3096	$1,064.31	$1,064.30	$1,064.30