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	$191.29	12.659%	$215.5054	$215.51	$215.50	$215.50
Purchase #2	$45.81	6.814%	$48.9315	$48.93	$48.95	$48.90
Purchase #3	$135.84	3.828%	$141.04	$141.04	$141.05	$141.00
Purchase #4	$72.81	11.222%	$80.9807	$80.98	$81.00	$81.00
Purchase #5	$85.69	6.454%	$91.2204	$91.22	$91.20	$91.20
Purchase #6	$196.65	11.554%	$219.3709	$219.37	$219.35	$219.40
Purchase #7	$146.88	13.240%	$166.3269	$166.33	$166.35	$166.30
7 purchase totals =	$874.97		$963.3758	$963.38	$963.40	$963.30