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	$47.69	12.275%	$53.5439	$53.54	$53.55	$53.50
Purchase #2	$129.25	9.547%	$141.5895	$141.59	$141.60	$141.60
Purchase #3	$82.50	4.138%	$85.9139	$85.91	$85.90	$85.90
Purchase #4	$62.67	9.134%	$68.3943	$68.39	$68.40	$68.40
Purchase #5	$229.34	5.318%	$241.5363	$241.54	$241.55	$241.50
Purchase #6	$182.71	12.464%	$205.483	$205.48	$205.50	$205.50
Purchase #7	$83.65	7.531%	$89.9497	$89.95	$89.95	$89.90
7 purchase totals =	$817.81		$886.4106	$886.40	$886.45	$886.30