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	$101.27	10.162%	$111.5611	$111.56	$111.55	$111.60
Purchase #2	$232.84	9.107%	$254.0447	$254.04	$254.05	$254.00
Purchase #3	$92.50	7.517%	$99.4532	$99.45	$99.45	$99.50
Purchase #4	$242.46	5.276%	$255.2522	$255.25	$255.25	$255.30
Purchase #5	$24.68	9.851%	$27.1112	$27.11	$27.10	$27.10
Purchase #6	$236.71	7.429%	$254.2952	$254.30	$254.30	$254.30
Purchase #7	$228.84	12.286%	$256.9553	$256.96	$256.95	$257.00
7 purchase totals =	$1,159.30		$1,258.6729	$1,258.67	$1,258.65	$1,258.80