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	$209.91	6.411%	$223.3673	$223.37	$223.35	$223.40
Purchase #2	$219.30	9.695%	$240.5611	$240.56	$240.55	$240.60
Purchase #3	$17.88	13.508%	$20.2952	$20.30	$20.30	$20.30
Purchase #4	$142.32	6.674%	$151.8184	$151.82	$151.80	$151.80
Purchase #5	$116.51	5.826%	$123.2979	$123.30	$123.30	$123.30
Purchase #6	$224.59	4.553%	$234.8156	$234.82	$234.80	$234.80
Purchase #7	$234.27	9.370%	$256.2211	$256.22	$256.20	$256.20
7 purchase totals =	$1,164.78		$1,250.3766	$1,250.39	$1,250.30	$1,250.40