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	$67.67	8.453%	$73.3901	$73.39	$73.40	$73.40
Purchase #2	$37.95	11.124%	$42.1716	$42.17	$42.15	$42.20
Purchase #3	$111.97	6.573%	$119.3298	$119.33	$119.35	$119.30
Purchase #4	$117.89	6.667%	$125.7497	$125.75	$125.75	$125.70
Purchase #5	$109.93	4.547%	$114.9285	$114.93	$114.95	$114.90
Purchase #6	$137.77	4.720%	$144.2727	$144.27	$144.25	$144.30
Purchase #7	$11.69	7.275%	$12.5404	$12.54	$12.55	$12.50
7 purchase totals =	$594.87		$632.3828	$632.38	$632.40	$632.30