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	$61.50	4.293%	$64.1402	$64.14	$64.15	$64.10
Purchase #2	$228.30	6.345%	$242.7856	$242.79	$242.80	$242.80
Purchase #3	$35.61	13.843%	$40.5395	$40.54	$40.55	$40.50
Purchase #4	$165.80	7.558%	$178.3312	$178.33	$178.35	$178.30
Purchase #5	$188.65	4.210%	$196.5922	$196.59	$196.60	$196.60
Purchase #6	$80.44	9.495%	$88.0778	$88.08	$88.10	$88.10
Purchase #7	$165.80	6.249%	$176.1608	$176.16	$176.15	$176.20
7 purchase totals =	$926.10		$986.6273	$986.63	$986.70	$986.60