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	$111.86	5.633%	$118.1611	$118.16	$118.15	$118.20
Purchase #2	$41.53	5.624%	$43.8656	$43.87	$43.85	$43.90
Purchase #3	$59.78	11.619%	$66.7258	$66.73	$66.75	$66.70
Purchase #4	$201.76	9.180%	$220.2816	$220.28	$220.30	$220.30
Purchase #5	$103.43	12.802%	$116.6711	$116.67	$116.65	$116.70
Purchase #6	$219.86	10.675%	$243.3301	$243.33	$243.35	$243.30
Purchase #7	$240.45	3.344%	$248.4906	$248.49	$248.50	$248.50
7 purchase totals =	$978.67		$1,057.5259	$1,057.53	$1,057.55	$1,057.60