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	$165.72	4.683%	$173.4807	$173.48	$173.50	$173.50
Purchase #2	$236.49	8.696%	$257.0552	$257.06	$257.05	$257.10
Purchase #3	$227.76	11.577%	$254.1278	$254.13	$254.15	$254.10
Purchase #4	$88.66	3.551%	$91.8083	$91.81	$91.80	$91.80
Purchase #5	$95.40	3.377%	$98.6217	$98.62	$98.60	$98.60
Purchase #6	$179.88	4.293%	$187.6022	$187.60	$187.60	$187.60
Purchase #7	$38.70	4.173%	$40.315	$40.32	$40.30	$40.30
7 purchase totals =	$1,032.61		$1,103.0109	$1,103.02	$1,103.00	$1,103.00