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	$41.61	3.774%	$43.1804	$43.18	$43.20	$43.20
Purchase #2	$100.88	8.270%	$109.2228	$109.22	$109.20	$109.20
Purchase #3	$200.76	4.215%	$209.222	$209.22	$209.20	$209.20
Purchase #4	$127.57	11.759%	$142.571	$142.57	$142.55	$142.60
Purchase #5	$27.68	5.504%	$29.2035	$29.20	$29.20	$29.20
Purchase #6	$141.66	8.653%	$153.9178	$153.92	$153.90	$153.90
Purchase #7	$93.30	11.770%	$104.2814	$104.28	$104.30	$104.30
7 purchase totals =	$733.46		$791.5989	$791.59	$791.55	$791.60