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	$32.92	7.397%	$35.3551	$35.36	$35.35	$35.40
Purchase #2	$200.34	13.607%	$227.6003	$227.60	$227.60	$227.60
Purchase #3	$86.65	13.794%	$98.6025	$98.60	$98.60	$98.60
Purchase #4	$58.81	11.113%	$65.3456	$65.35	$65.35	$65.30
Purchase #5	$116.40	9.273%	$127.1938	$127.19	$127.20	$127.20
Purchase #6	$131.49	8.227%	$142.3077	$142.31	$142.30	$142.30
Purchase #7	$82.65	12.711%	$93.1556	$93.16	$93.15	$93.20
7 purchase totals =	$709.26		$789.5606	$789.57	$789.55	$789.60