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	$222.46	9.118%	$242.7439	$242.74	$242.75	$242.70
Purchase #2	$167.82	9.403%	$183.6001	$183.60	$183.60	$183.60
Purchase #3	$238.37	7.525%	$256.3073	$256.31	$256.30	$256.30
Purchase #4	$41.94	7.346%	$45.0209	$45.02	$45.00	$45.00
Purchase #5	$94.49	11.811%	$105.6502	$105.65	$105.65	$105.70
Purchase #6	$82.61	9.341%	$90.3266	$90.33	$90.35	$90.30
Purchase #7	$70.77	13.519%	$80.3374	$80.34	$80.35	$80.30
7 purchase totals =	$918.46		$1,003.9864	$1,003.99	$1,004.00	$1,003.90