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	$112.33	4.782%	$117.7016	$117.70	$117.70	$117.70
Purchase #2	$170.98	9.127%	$186.5853	$186.59	$186.60	$186.60
Purchase #3	$124.61	5.254%	$131.157	$131.16	$131.15	$131.20
Purchase #4	$65.62	3.123%	$67.6693	$67.67	$67.65	$67.70
Purchase #5	$82.97	4.170%	$86.4298	$86.43	$86.45	$86.40
Purchase #6	$244.53	4.856%	$256.4044	$256.40	$256.40	$256.40
Purchase #7	$67.51	6.769%	$72.0798	$72.08	$72.10	$72.10
7 purchase totals =	$868.55		$918.0272	$918.03	$918.05	$918.10