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	$62.48	10.568%	$69.0829	$69.08	$69.10	$69.10
Purchase #2	$213.78	13.429%	$242.4885	$242.49	$242.50	$242.50
Purchase #3	$230.27	6.479%	$245.1892	$245.19	$245.20	$245.20
Purchase #4	$103.93	5.203%	$109.3375	$109.34	$109.35	$109.30
Purchase #5	$244.76	8.156%	$264.7226	$264.72	$264.70	$264.70
Purchase #6	$79.29	13.309%	$89.8427	$89.84	$89.85	$89.80
Purchase #7	$187.85	4.606%	$196.5024	$196.50	$196.50	$196.50
7 purchase totals =	$1,122.36		$1,217.1658	$1,217.16	$1,217.20	$1,217.10