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	$134.87	4.343%	$140.7274	$140.73	$140.75	$140.70
Purchase #2	$52.62	3.839%	$54.6401	$54.64	$54.65	$54.60
Purchase #3	$172.32	10.120%	$189.7588	$189.76	$189.75	$189.80
Purchase #4	$130.76	5.445%	$137.8799	$137.88	$137.90	$137.90
Purchase #5	$215.67	5.221%	$226.9301	$226.93	$226.95	$226.90
Purchase #6	$168.59	8.445%	$182.8274	$182.83	$182.85	$182.80
Purchase #7	$107.90	3.195%	$111.3474	$111.35	$111.35	$111.30
7 purchase totals =	$982.73		$1,044.1111	$1,044.12	$1,044.20	$1,044.00