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	$127.83	7.647%	$137.6052	$137.61	$137.60	$137.60
Purchase #2	$187.55	9.789%	$205.9093	$205.91	$205.90	$205.90
Purchase #3	$43.48	5.155%	$45.7214	$45.72	$45.70	$45.70
Purchase #4	$150.92	11.781%	$168.6999	$168.70	$168.70	$168.70
Purchase #5	$106.66	3.435%	$110.3238	$110.32	$110.30	$110.30
Purchase #6	$91.74	8.872%	$99.8792	$99.88	$99.90	$99.90
Purchase #7	$110.62	7.696%	$119.1333	$119.13	$119.15	$119.10
7 purchase totals =	$818.80		$887.2721	$887.27	$887.25	$887.20