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	$88.94	8.565%	$96.5577	$96.56	$96.55	$96.60
Purchase #2	$128.46	9.816%	$141.0696	$141.07	$141.05	$141.10
Purchase #3	$5.49	13.308%	$6.2206	$6.22	$6.20	$6.20
Purchase #4	$13.98	6.168%	$14.8423	$14.84	$14.85	$14.80
Purchase #5	$62.74	5.258%	$66.0389	$66.04	$66.05	$66.00
Purchase #6	$109.79	12.416%	$123.4215	$123.42	$123.40	$123.40
Purchase #7	$67.92	7.209%	$72.8164	$72.82	$72.80	$72.80
7 purchase totals =	$477.32		$520.9670	$520.97	$520.90	$520.90