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	$147.70	7.340%	$158.5412	$158.54	$158.55	$158.50
Purchase #2	$103.91	5.765%	$109.9004	$109.90	$109.90	$109.90
Purchase #3	$59.52	5.352%	$62.7055	$62.71	$62.70	$62.70
Purchase #4	$127.37	4.640%	$133.28	$133.28	$133.30	$133.30
Purchase #5	$150.41	10.673%	$166.4633	$166.46	$166.45	$166.50
Purchase #6	$39.51	4.182%	$41.1623	$41.16	$41.15	$41.20
Purchase #7	$129.38	3.120%	$133.4167	$133.42	$133.40	$133.40
7 purchase totals =	$757.80		$805.4694	$805.47	$805.45	$805.50