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	$84.51	5.814%	$89.4234	$89.42	$89.40	$89.40
Purchase #2	$104.55	3.395%	$108.0995	$108.10	$108.10	$108.10
Purchase #3	$152.81	7.775%	$164.691	$164.69	$164.70	$164.70
Purchase #4	$74.82	6.510%	$79.6908	$79.69	$79.70	$79.70
Purchase #5	$127.30	13.343%	$144.2856	$144.29	$144.30	$144.30
Purchase #6	$227.79	5.162%	$239.5485	$239.55	$239.55	$239.50
Purchase #7	$182.28	9.587%	$199.7552	$199.76	$199.75	$199.80
7 purchase totals =	$954.06		$1,025.4940	$1,025.50	$1,025.50	$1,025.50