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	$48.52	11.499%	$54.0993	$54.10	$54.10	$54.10
Purchase #2	$58.57	5.460%	$61.7679	$61.77	$61.75	$61.80
Purchase #3	$223.88	12.359%	$251.5493	$251.55	$251.55	$251.50
Purchase #4	$135.89	6.603%	$144.8628	$144.86	$144.85	$144.90
Purchase #5	$22.36	9.729%	$24.5354	$24.54	$24.55	$24.50
Purchase #6	$54.85	13.519%	$62.2652	$62.27	$62.25	$62.30
Purchase #7	$105.60	9.172%	$115.2856	$115.29	$115.30	$115.30
7 purchase totals =	$649.67		$714.3655	$714.38	$714.35	$714.40