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	$187.68	3.535%	$194.3145	$194.31	$194.30	$194.30
Purchase #2	$96.40	3.283%	$99.5648	$99.56	$99.55	$99.60
Purchase #3	$143.30	11.584%	$159.8999	$159.90	$159.90	$159.90
Purchase #4	$243.89	11.426%	$271.7569	$271.76	$271.75	$271.80
Purchase #5	$22.30	5.661%	$23.5624	$23.56	$23.55	$23.60
Purchase #6	$61.70	8.409%	$66.8884	$66.89	$66.90	$66.90
Purchase #7	$250.27	8.162%	$270.697	$270.70	$270.70	$270.70
7 purchase totals =	$1,005.54		$1,086.6839	$1,086.68	$1,086.65	$1,086.80