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	$44.56	8.460%	$48.3298	$48.33	$48.35	$48.30
Purchase #2	$89.92	11.202%	$99.9928	$99.99	$100.00	$100.00
Purchase #3	$22.73	8.179%	$24.5891	$24.59	$24.60	$24.60
Purchase #4	$122.59	7.132%	$131.3331	$131.33	$131.35	$131.30
Purchase #5	$238.51	10.256%	$262.9716	$262.97	$262.95	$263.00
Purchase #6	$220.40	6.116%	$233.8797	$233.88	$233.90	$233.90
Purchase #7	$147.71	4.338%	$154.1177	$154.12	$154.10	$154.10
7 purchase totals =	$886.42		$955.2138	$955.21	$955.25	$955.20