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	$180.62	5.202%	$190.0159	$190.02	$190.00	$190.00
Purchase #2	$17.33	10.173%	$19.093	$19.09	$19.10	$19.10
Purchase #3	$150.39	10.200%	$165.7298	$165.73	$165.75	$165.70
Purchase #4	$249.41	11.476%	$278.0323	$278.03	$278.05	$278.00
Purchase #5	$250.74	11.493%	$279.5575	$279.56	$279.55	$279.60
Purchase #6	$37.38	11.207%	$41.5692	$41.57	$41.55	$41.60
Purchase #7	$27.68	13.784%	$31.4954	$31.50	$31.50	$31.50
7 purchase totals =	$913.55		$1,005.4931	$1,005.50	$1,005.50	$1,005.50