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	$100.62	3.645%	$104.2876	$104.29	$104.30	$104.30
Purchase #2	$109.35	3.257%	$112.9115	$112.91	$112.90	$112.90
Purchase #3	$162.37	8.708%	$176.5092	$176.51	$176.50	$176.50
Purchase #4	$187.29	6.778%	$199.9845	$199.98	$200.00	$200.00
Purchase #5	$86.32	3.171%	$89.0572	$89.06	$89.05	$89.10
Purchase #6	$106.31	11.647%	$118.6919	$118.69	$118.70	$118.70
Purchase #7	$106.97	5.753%	$113.124	$113.12	$113.10	$113.10
7 purchase totals =	$859.23		$914.5659	$914.56	$914.55	$914.60