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	$85.85	10.467%	$94.8359	$94.84	$94.85	$94.80
Purchase #2	$249.60	3.391%	$258.0639	$258.06	$258.05	$258.10
Purchase #3	$207.47	5.205%	$218.2688	$218.27	$218.25	$218.30
Purchase #4	$124.39	10.366%	$137.2843	$137.28	$137.30	$137.30
Purchase #5	$35.78	3.470%	$37.0216	$37.02	$37.00	$37.00
Purchase #6	$11.55	11.478%	$12.8757	$12.88	$12.90	$12.90
Purchase #7	$215.89	13.471%	$244.9725	$244.97	$244.95	$245.00
7 purchase totals =	$930.53		$1,003.3227	$1,003.32	$1,003.30	$1,003.40