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	$189.70	5.295%	$199.7446	$199.74	$199.75	$199.70
Purchase #2	$131.63	12.361%	$147.9008	$147.90	$147.90	$147.90
Purchase #3	$65.43	10.335%	$72.1922	$72.19	$72.20	$72.20
Purchase #4	$90.55	6.535%	$96.4674	$96.47	$96.45	$96.50
Purchase #5	$102.44	9.421%	$112.0909	$112.09	$112.10	$112.10
Purchase #6	$246.94	11.287%	$274.8121	$274.81	$274.80	$274.80
Purchase #7	$175.35	9.450%	$191.9206	$191.92	$191.90	$191.90
7 purchase totals =	$1,002.04		$1,095.1286	$1,095.12	$1,095.10	$1,095.10