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	$143.48	12.140%	$160.8985	$160.90	$160.90	$160.90
Purchase #2	$68.90	4.853%	$72.2437	$72.24	$72.25	$72.20
Purchase #3	$250.33	6.403%	$266.3586	$266.36	$266.35	$266.40
Purchase #4	$87.84	4.132%	$91.4695	$91.47	$91.45	$91.50
Purchase #5	$245.63	7.579%	$264.2463	$264.25	$264.25	$264.20
Purchase #6	$38.73	7.766%	$41.7378	$41.74	$41.75	$41.70
Purchase #7	$49.34	9.363%	$53.9597	$53.96	$53.95	$54.00
7 purchase totals =	$884.25		$950.9141	$950.92	$950.90	$950.90