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	$69.75	9.571%	$76.4258	$76.43	$76.45	$76.40
Purchase #2	$174.27	9.843%	$191.4234	$191.42	$191.40	$191.40
Purchase #3	$191.97	12.818%	$216.5767	$216.58	$216.60	$216.60
Purchase #4	$156.30	10.307%	$172.4098	$172.41	$172.40	$172.40
Purchase #5	$54.60	8.459%	$59.2186	$59.22	$59.20	$59.20
Purchase #6	$104.92	13.129%	$118.6949	$118.69	$118.70	$118.70
Purchase #7	$239.62	10.159%	$263.963	$263.96	$263.95	$264.00
7 purchase totals =	$991.43		$1,098.7122	$1,098.71	$1,098.70	$1,098.70