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	$111.82	6.459%	$119.0425	$119.04	$119.05	$119.00
Purchase #2	$129.94	8.573%	$141.0798	$141.08	$141.10	$141.10
Purchase #3	$152.86	6.566%	$162.8968	$162.90	$162.90	$162.90
Purchase #4	$96.46	4.386%	$100.6907	$100.69	$100.70	$100.70
Purchase #5	$198.92	8.209%	$215.2493	$215.25	$215.25	$215.20
Purchase #6	$250.53	10.521%	$276.8883	$276.89	$276.90	$276.90
Purchase #7	$144.36	7.508%	$155.1985	$155.20	$155.20	$155.20
7 purchase totals =	$1,084.89		$1,171.0459	$1,171.05	$1,171.10	$1,171.00