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	$167.55	9.770%	$183.9196	$183.92	$183.90	$183.90
Purchase #2	$129.61	9.254%	$141.6041	$141.60	$141.60	$141.60
Purchase #3	$239.30	10.601%	$264.6682	$264.67	$264.65	$264.70
Purchase #4	$186.52	12.522%	$209.876	$209.88	$209.90	$209.90
Purchase #5	$83.31	13.288%	$94.3802	$94.38	$94.40	$94.40
Purchase #6	$230.73	4.437%	$240.9675	$240.97	$240.95	$241.00
Purchase #7	$180.64	8.727%	$196.4045	$196.40	$196.40	$196.40
7 purchase totals =	$1,217.66		$1,331.8201	$1,331.82	$1,331.80	$1,331.90