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	$69.36	7.401%	$74.4933	$74.49	$74.50	$74.50
Purchase #2	$39.54	7.635%	$42.5589	$42.56	$42.55	$42.60
Purchase #3	$160.45	8.687%	$174.3883	$174.39	$174.40	$174.40
Purchase #4	$38.41	11.638%	$42.8802	$42.88	$42.90	$42.90
Purchase #5	$151.48	13.527%	$171.9707	$171.97	$171.95	$172.00
Purchase #6	$174.45	12.468%	$196.2004	$196.20	$196.20	$196.20
Purchase #7	$207.53	11.263%	$230.9041	$230.90	$230.90	$230.90
7 purchase totals =	$841.22		$933.3959	$933.39	$933.40	$933.50