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	$101.54	4.411%	$106.0189	$106.02	$106.00	$106.00
Purchase #2	$215.99	3.650%	$223.8736	$223.87	$223.85	$223.90
Purchase #3	$118.85	4.234%	$123.8821	$123.88	$123.90	$123.90
Purchase #4	$179.97	6.456%	$191.5889	$191.59	$191.60	$191.60
Purchase #5	$137.98	12.691%	$155.491	$155.49	$155.50	$155.50
Purchase #6	$107.93	4.105%	$112.3605	$112.36	$112.35	$112.40
Purchase #7	$243.49	5.199%	$256.149	$256.15	$256.15	$256.10
7 purchase totals =	$1,105.75		$1,169.3640	$1,169.36	$1,169.35	$1,169.40