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	$194.91	4.788%	$204.2423	$204.24	$204.25	$204.20
Purchase #2	$65.82	8.198%	$71.2159	$71.22	$71.20	$71.20
Purchase #3	$142.44	11.242%	$158.4531	$158.45	$158.45	$158.50
Purchase #4	$127.50	12.862%	$143.8991	$143.90	$143.90	$143.90
Purchase #5	$193.98	8.661%	$210.7806	$210.78	$210.80	$210.80
Purchase #6	$73.33	12.557%	$82.538	$82.54	$82.55	$82.50
Purchase #7	$49.83	5.122%	$52.3823	$52.38	$52.40	$52.40
7 purchase totals =	$847.81		$923.5113	$923.51	$923.55	$923.50