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	$225.75	4.518%	$235.9494	$235.95	$235.95	$235.90
Purchase #2	$91.44	13.356%	$103.6527	$103.65	$103.65	$103.70
Purchase #3	$39.36	11.836%	$44.0186	$44.02	$44.00	$44.00
Purchase #4	$169.59	10.726%	$187.7802	$187.78	$187.80	$187.80
Purchase #5	$113.92	11.152%	$126.6244	$126.62	$126.60	$126.60
Purchase #6	$249.50	10.537%	$275.7898	$275.79	$275.80	$275.80
Purchase #7	$116.44	9.151%	$127.0954	$127.10	$127.10	$127.10
7 purchase totals =	$1,006.00		$1,100.9105	$1,100.91	$1,100.90	$1,100.90