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	$67.57	11.740%	$75.5027	$75.50	$75.50	$75.50
Purchase #2	$17.76	4.135%	$18.4944	$18.49	$18.50	$18.50
Purchase #3	$117.31	12.111%	$131.5174	$131.52	$131.50	$131.50
Purchase #4	$216.73	4.695%	$226.9055	$226.91	$226.90	$226.90
Purchase #5	$211.82	13.417%	$240.2399	$240.24	$240.25	$240.20
Purchase #6	$177.98	9.854%	$195.5181	$195.52	$195.50	$195.50
Purchase #7	$42.65	6.443%	$45.3979	$45.40	$45.40	$45.40
7 purchase totals =	$851.82		$933.5759	$933.58	$933.55	$933.50