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	$187.67	10.784%	$207.9083	$207.91	$207.90	$207.90
Purchase #2	$224.28	7.107%	$240.2196	$240.22	$240.20	$240.20
Purchase #3	$50.57	7.474%	$54.3496	$54.35	$54.35	$54.30
Purchase #4	$236.48	9.675%	$259.3594	$259.36	$259.35	$259.40
Purchase #5	$149.72	8.687%	$162.7262	$162.73	$162.75	$162.70
Purchase #6	$107.83	3.160%	$111.2374	$111.24	$111.25	$111.20
Purchase #7	$7.28	4.583%	$7.6136	$7.61	$7.60	$7.60
7 purchase totals =	$963.83		$1,043.4141	$1,043.42	$1,043.40	$1,043.30