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	$33.99	4.707%	$35.5899	$35.59	$35.60	$35.60
Purchase #2	$204.31	11.243%	$227.2806	$227.28	$227.30	$227.30
Purchase #3	$43.75	6.390%	$46.5456	$46.55	$46.55	$46.50
Purchase #4	$177.40	5.354%	$186.898	$186.90	$186.90	$186.90
Purchase #5	$123.82	5.459%	$130.5793	$130.58	$130.60	$130.60
Purchase #6	$238.48	10.383%	$263.2414	$263.24	$263.25	$263.20
Purchase #7	$64.46	13.124%	$72.9197	$72.92	$72.90	$72.90
7 purchase totals =	$886.21		$963.0545	$963.06	$963.10	$963.00