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	$211.27	13.777%	$240.3767	$240.38	$240.40	$240.40
Purchase #2	$24.43	7.383%	$26.2337	$26.23	$26.25	$26.20
Purchase #3	$213.38	4.501%	$222.9842	$222.98	$223.00	$223.00
Purchase #4	$61.70	6.814%	$65.9042	$65.90	$65.90	$65.90
Purchase #5	$73.62	8.552%	$79.916	$79.92	$79.90	$79.90
Purchase #6	$40.54	12.492%	$45.6043	$45.60	$45.60	$45.60
Purchase #7	$62.70	7.478%	$67.3887	$67.39	$67.40	$67.40
7 purchase totals =	$687.64		$748.4078	$748.40	$748.45	$748.40