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	$132.42	4.760%	$138.7232	$138.72	$138.70	$138.70
Purchase #2	$173.63	13.201%	$196.5509	$196.55	$196.55	$196.60
Purchase #3	$59.81	13.146%	$67.6726	$67.67	$67.65	$67.70
Purchase #4	$212.96	6.239%	$226.2466	$226.25	$226.25	$226.20
Purchase #5	$191.84	7.838%	$206.8764	$206.88	$206.90	$206.90
Purchase #6	$99.57	13.322%	$112.8347	$112.83	$112.85	$112.80
Purchase #7	$90.42	9.626%	$99.1238	$99.12	$99.10	$99.10
7 purchase totals =	$960.65		$1,048.0282	$1,048.02	$1,048.00	$1,048.00