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	$171.57	11.594%	$191.4618	$191.46	$191.45	$191.50
Purchase #2	$109.86	5.244%	$115.6211	$115.62	$115.60	$115.60
Purchase #3	$24.35	5.337%	$25.6496	$25.65	$25.65	$25.60
Purchase #4	$91.49	11.118%	$101.6619	$101.66	$101.65	$101.70
Purchase #5	$112.80	3.157%	$116.3611	$116.36	$116.35	$116.40
Purchase #6	$115.67	13.685%	$131.4994	$131.50	$131.50	$131.50
Purchase #7	$153.55	5.547%	$162.0674	$162.07	$162.05	$162.10
7 purchase totals =	$779.29		$844.3223	$844.32	$844.25	$844.40