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	$125.60	13.251%	$142.2433	$142.24	$142.25	$142.20
Purchase #2	$138.67	8.573%	$150.5582	$150.56	$150.55	$150.60
Purchase #3	$141.73	6.447%	$150.8673	$150.87	$150.85	$150.90
Purchase #4	$197.99	7.796%	$213.4253	$213.43	$213.45	$213.40
Purchase #5	$40.63	11.382%	$45.2545	$45.25	$45.25	$45.30
Purchase #6	$84.66	7.362%	$90.8927	$90.89	$90.90	$90.90
Purchase #7	$213.64	7.112%	$228.8341	$228.83	$228.85	$228.80
7 purchase totals =	$942.92		$1,022.0754	$1,022.07	$1,022.10	$1,022.10