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	$82.51	9.298%	$90.1818	$90.18	$90.20	$90.20
Purchase #2	$107.61	3.128%	$110.976	$110.98	$111.00	$111.00
Purchase #3	$167.89	6.751%	$179.2243	$179.22	$179.20	$179.20
Purchase #4	$11.44	7.298%	$12.2749	$12.27	$12.25	$12.30
Purchase #5	$39.72	8.794%	$43.213	$43.21	$43.20	$43.20
Purchase #6	$146.71	6.873%	$156.7934	$156.79	$156.80	$156.80
Purchase #7	$210.32	5.446%	$221.774	$221.77	$221.75	$221.80
7 purchase totals =	$766.20		$814.4374	$814.42	$814.40	$814.50