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	$142.60	11.178%	$158.5398	$158.54	$158.55	$158.50
Purchase #2	$38.79	13.675%	$44.0945	$44.09	$44.10	$44.10
Purchase #3	$93.30	8.160%	$100.9133	$100.91	$100.90	$100.90
Purchase #4	$117.42	13.857%	$133.6909	$133.69	$133.70	$133.70
Purchase #5	$250.88	3.276%	$259.0988	$259.10	$259.10	$259.10
Purchase #6	$117.79	11.543%	$131.3865	$131.39	$131.40	$131.40
Purchase #7	$94.78	5.315%	$99.8176	$99.82	$99.80	$99.80
7 purchase totals =	$855.56		$927.5414	$927.54	$927.55	$927.50