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	$68.76	10.604%	$76.0513	$76.05	$76.05	$76.10
Purchase #2	$243.38	10.741%	$269.5214	$269.52	$269.50	$269.50
Purchase #3	$167.92	3.178%	$173.2565	$173.26	$173.25	$173.30
Purchase #4	$50.96	6.274%	$54.1572	$54.16	$54.15	$54.20
Purchase #5	$30.33	11.159%	$33.7145	$33.71	$33.70	$33.70
Purchase #6	$109.29	4.468%	$114.1731	$114.17	$114.15	$114.20
Purchase #7	$19.52	9.807%	$21.4343	$21.43	$21.45	$21.40
7 purchase totals =	$690.16		$742.3083	$742.30	$742.25	$742.40