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	$111.44	4.114%	$116.0246	$116.02	$116.00	$116.00
Purchase #2	$148.29	5.267%	$156.1004	$156.10	$156.10	$156.10
Purchase #3	$76.81	8.525%	$83.3581	$83.36	$83.35	$83.40
Purchase #4	$170.76	11.565%	$190.5084	$190.51	$190.50	$190.50
Purchase #5	$30.87	9.424%	$33.7792	$33.78	$33.80	$33.80
Purchase #6	$29.64	11.346%	$33.003	$33.00	$33.00	$33.00
Purchase #7	$164.56	13.796%	$187.2627	$187.26	$187.25	$187.30
7 purchase totals =	$732.37		$800.0364	$800.03	$800.00	$800.10