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	$33.36	6.548%	$35.5444	$35.54	$35.55	$35.50
Purchase #2	$89.93	9.410%	$98.3924	$98.39	$98.40	$98.40
Purchase #3	$146.61	10.765%	$162.3926	$162.39	$162.40	$162.40
Purchase #4	$14.55	12.619%	$16.3861	$16.39	$16.40	$16.40
Purchase #5	$17.79	5.630%	$18.7916	$18.79	$18.80	$18.80
Purchase #6	$180.49	5.500%	$190.417	$190.42	$190.40	$190.40
Purchase #7	$168.82	9.754%	$185.2867	$185.29	$185.30	$185.30
7 purchase totals =	$651.55		$707.2108	$707.21	$707.25	$707.20