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	$84.89	5.672%	$89.705	$89.71	$89.70	$89.70
Purchase #2	$149.72	3.472%	$154.9183	$154.92	$154.90	$154.90
Purchase #3	$172.71	13.756%	$196.468	$196.47	$196.45	$196.50
Purchase #4	$138.87	13.405%	$157.4855	$157.49	$157.50	$157.50
Purchase #5	$177.82	4.846%	$186.4372	$186.44	$186.45	$186.40
Purchase #6	$128.25	12.869%	$144.7545	$144.75	$144.75	$144.80
Purchase #7	$132.33	12.839%	$149.3198	$149.32	$149.30	$149.30
7 purchase totals =	$984.59		$1,079.0883	$1,079.10	$1,079.05	$1,079.10