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	$70.96	4.717%	$74.3072	$74.31	$74.30	$74.30
Purchase #2	$61.80	12.594%	$69.5831	$69.58	$69.60	$69.60
Purchase #3	$52.90	8.758%	$57.533	$57.53	$57.55	$57.50
Purchase #4	$156.74	11.210%	$174.3106	$174.31	$174.30	$174.30
Purchase #5	$222.83	12.482%	$250.6436	$250.64	$250.65	$250.60
Purchase #6	$174.44	12.785%	$196.7422	$196.74	$196.75	$196.70
Purchase #7	$128.94	10.397%	$142.3459	$142.35	$142.35	$142.30
7 purchase totals =	$868.61		$965.4656	$965.46	$965.50	$965.30