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	$92.34	11.322%	$102.7947	$102.79	$102.80	$102.80
Purchase #2	$242.61	7.627%	$261.1139	$261.11	$261.10	$261.10
Purchase #3	$69.58	7.751%	$74.9731	$74.97	$74.95	$75.00
Purchase #4	$42.52	10.287%	$46.894	$46.89	$46.90	$46.90
Purchase #5	$145.98	8.612%	$158.5518	$158.55	$158.55	$158.60
Purchase #6	$116.59	12.463%	$131.1206	$131.12	$131.10	$131.10
Purchase #7	$91.28	9.639%	$100.0785	$100.08	$100.10	$100.10
7 purchase totals =	$800.90		$875.5266	$875.51	$875.50	$875.60