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	$162.87	3.690%	$168.8799	$168.88	$168.90	$168.90
Purchase #2	$35.91	12.172%	$40.281	$40.28	$40.30	$40.30
Purchase #3	$73.97	10.611%	$81.819	$81.82	$81.80	$81.80
Purchase #4	$85.36	10.444%	$94.275	$94.28	$94.30	$94.30
Purchase #5	$97.49	4.527%	$101.9034	$101.90	$101.90	$101.90
Purchase #6	$161.39	10.857%	$178.9121	$178.91	$178.90	$178.90
Purchase #7	$156.82	6.360%	$166.7938	$166.79	$166.80	$166.80
7 purchase totals =	$773.81		$832.8642	$832.86	$832.90	$832.90