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	$95.26	3.470%	$98.5655	$98.57	$98.55	$98.60
Purchase #2	$103.83	10.463%	$114.6937	$114.69	$114.70	$114.70
Purchase #3	$209.89	7.700%	$226.0515	$226.05	$226.05	$226.10
Purchase #4	$22.98	10.299%	$25.3467	$25.35	$25.35	$25.30
Purchase #5	$126.84	7.581%	$136.4557	$136.46	$136.45	$136.50
Purchase #6	$92.30	8.167%	$99.8381	$99.84	$99.85	$99.80
Purchase #7	$148.50	12.764%	$167.4545	$167.45	$167.45	$167.50
7 purchase totals =	$799.60		$868.4057	$868.41	$868.40	$868.50