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	$83.48	7.442%	$89.6926	$89.69	$89.70	$89.70
Purchase #2	$141.65	7.363%	$152.0797	$152.08	$152.10	$152.10
Purchase #3	$160.76	8.569%	$174.5355	$174.54	$174.55	$174.50
Purchase #4	$35.33	9.361%	$38.6372	$38.64	$38.65	$38.60
Purchase #5	$171.64	5.856%	$181.6912	$181.69	$181.70	$181.70
Purchase #6	$247.45	10.432%	$273.264	$273.26	$273.25	$273.30
Purchase #7	$132.84	6.435%	$141.3883	$141.39	$141.40	$141.40
7 purchase totals =	$973.15		$1,051.2885	$1,051.29	$1,051.35	$1,051.30