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	$106.83	9.625%	$117.1124	$117.11	$117.10	$117.10
Purchase #2	$45.57	3.674%	$47.2442	$47.24	$47.25	$47.20
Purchase #3	$43.61	5.233%	$45.8921	$45.89	$45.90	$45.90
Purchase #4	$134.74	5.108%	$141.6225	$141.62	$141.60	$141.60
Purchase #5	$213.54	9.826%	$234.5224	$234.52	$234.50	$234.50
Purchase #6	$216.69	7.756%	$233.4965	$233.50	$233.50	$233.50
Purchase #7	$133.78	13.827%	$152.2778	$152.28	$152.30	$152.30
7 purchase totals =	$894.76		$972.1679	$972.16	$972.15	$972.10