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	$31.59	7.360%	$33.915	$33.92	$33.90	$33.90
Purchase #2	$9.55	6.373%	$10.1586	$10.16	$10.15	$10.20
Purchase #3	$42.29	7.173%	$45.3235	$45.32	$45.30	$45.30
Purchase #4	$230.50	11.528%	$257.072	$257.07	$257.05	$257.10
Purchase #5	$183.64	9.236%	$200.601	$200.60	$200.60	$200.60
Purchase #6	$174.76	8.496%	$189.6076	$189.61	$189.60	$189.60
Purchase #7	$161.91	6.108%	$171.7995	$171.80	$171.80	$171.80
7 purchase totals =	$834.24		$908.4772	$908.48	$908.40	$908.50