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	$244.39	4.326%	$254.9623	$254.96	$254.95	$255.00
Purchase #2	$142.38	13.303%	$161.3208	$161.32	$161.30	$161.30
Purchase #3	$53.62	4.285%	$55.9176	$55.92	$55.90	$55.90
Purchase #4	$76.76	11.575%	$85.645	$85.65	$85.65	$85.60
Purchase #5	$211.92	10.572%	$234.3242	$234.32	$234.30	$234.30
Purchase #6	$248.38	8.508%	$269.5122	$269.51	$269.50	$269.50
Purchase #7	$131.31	8.440%	$142.3926	$142.39	$142.40	$142.40
7 purchase totals =	$1,108.76		$1,204.0747	$1,204.07	$1,204.00	$1,204.00