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	$223.27	8.133%	$241.4285	$241.43	$241.45	$241.40
Purchase #2	$197.69	6.131%	$209.8104	$209.81	$209.80	$209.80
Purchase #3	$38.79	12.825%	$43.7648	$43.76	$43.75	$43.80
Purchase #4	$250.32	13.662%	$284.5187	$284.52	$284.50	$284.50
Purchase #5	$34.54	8.486%	$37.4711	$37.47	$37.45	$37.50
Purchase #6	$16.38	5.516%	$17.2835	$17.28	$17.30	$17.30
Purchase #7	$92.31	9.674%	$101.2401	$101.24	$101.25	$101.20
7 purchase totals =	$853.30		$935.5171	$935.51	$935.50	$935.50