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	$106.85	10.678%	$118.2594	$118.26	$118.25	$118.30
Purchase #2	$242.59	6.618%	$258.6446	$258.64	$258.65	$258.60
Purchase #3	$54.62	9.710%	$59.9236	$59.92	$59.90	$59.90
Purchase #4	$99.47	3.665%	$103.1156	$103.12	$103.10	$103.10
Purchase #5	$136.49	9.496%	$149.4511	$149.45	$149.45	$149.50
Purchase #6	$203.48	12.465%	$228.8438	$228.84	$228.85	$228.80
Purchase #7	$187.57	13.699%	$213.2652	$213.27	$213.25	$213.30
7 purchase totals =	$1,031.07		$1,131.5033	$1,131.50	$1,131.45	$1,131.50