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	$32.74	8.457%	$35.5088	$35.51	$35.50	$35.50
Purchase #2	$211.29	3.336%	$218.3386	$218.34	$218.35	$218.30
Purchase #3	$61.41	9.762%	$67.4048	$67.40	$67.40	$67.40
Purchase #4	$16.40	9.859%	$18.0169	$18.02	$18.00	$18.00
Purchase #5	$134.29	13.166%	$151.9706	$151.97	$151.95	$152.00
Purchase #6	$40.73	5.383%	$42.9225	$42.92	$42.90	$42.90
Purchase #7	$230.98	8.437%	$250.4678	$250.47	$250.45	$250.50
7 purchase totals =	$727.84		$784.6300	$784.63	$784.55	$784.60