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	$51.63	10.111%	$56.8503	$56.85	$56.85	$56.90
Purchase #2	$188.53	9.213%	$205.8993	$205.90	$205.90	$205.90
Purchase #3	$110.36	5.483%	$116.411	$116.41	$116.40	$116.40
Purchase #4	$41.55	9.404%	$45.4574	$45.46	$45.45	$45.50
Purchase #5	$133.57	9.665%	$146.4795	$146.48	$146.50	$146.50
Purchase #6	$182.96	3.379%	$189.1422	$189.14	$189.15	$189.10
Purchase #7	$112.71	11.118%	$125.2411	$125.24	$125.25	$125.20
7 purchase totals =	$821.31		$885.4808	$885.48	$885.50	$885.50