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	$163.85	11.612%	$182.8763	$182.88	$182.90	$182.90
Purchase #2	$136.39	4.604%	$142.6694	$142.67	$142.65	$142.70
Purchase #3	$116.49	4.568%	$121.8113	$121.81	$121.80	$121.80
Purchase #4	$99.59	5.835%	$105.4011	$105.40	$105.40	$105.40
Purchase #5	$204.83	7.553%	$220.3008	$220.30	$220.30	$220.30
Purchase #6	$190.30	10.297%	$209.8952	$209.90	$209.90	$209.90
Purchase #7	$159.91	13.735%	$181.8736	$181.87	$181.85	$181.90
7 purchase totals =	$1,071.36		$1,164.8277	$1,164.83	$1,164.80	$1,164.90