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	$102.78	13.389%	$116.5412	$116.54	$116.55	$116.50
Purchase #2	$203.85	12.813%	$229.9693	$229.97	$229.95	$230.00
Purchase #3	$246.69	3.414%	$255.112	$255.11	$255.10	$255.10
Purchase #4	$113.62	4.465%	$118.6931	$118.69	$118.70	$118.70
Purchase #5	$76.33	9.108%	$83.2821	$83.28	$83.30	$83.30
Purchase #6	$111.70	4.600%	$116.8382	$116.84	$116.85	$116.80
Purchase #7	$115.72	9.352%	$126.5421	$126.54	$126.55	$126.50
7 purchase totals =	$970.69		$1,046.9780	$1,046.97	$1,047.00	$1,046.90