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	$136.38	4.164%	$142.0589	$142.06	$142.05	$142.10
Purchase #2	$88.82	11.736%	$99.2439	$99.24	$99.25	$99.20
Purchase #3	$81.63	4.668%	$85.4405	$85.44	$85.45	$85.40
Purchase #4	$100.84	10.550%	$111.4786	$111.48	$111.50	$111.50
Purchase #5	$232.91	11.153%	$258.8865	$258.89	$258.90	$258.90
Purchase #6	$84.83	12.432%	$95.3761	$95.38	$95.40	$95.40
Purchase #7	$197.43	3.617%	$204.571	$204.57	$204.55	$204.60
7 purchase totals =	$922.84		$997.0555	$997.06	$997.10	$997.10