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	$146.28	4.371%	$152.6739	$152.67	$152.65	$152.70
Purchase #2	$133.42	7.604%	$143.5653	$143.57	$143.55	$143.60
Purchase #3	$160.56	9.706%	$176.144	$176.14	$176.15	$176.10
Purchase #4	$182.63	7.321%	$196.0003	$196.00	$196.00	$196.00
Purchase #5	$180.69	13.717%	$205.4752	$205.48	$205.50	$205.50
Purchase #6	$97.72	12.154%	$109.5969	$109.60	$109.60	$109.60
Purchase #7	$149.70	3.750%	$155.3138	$155.31	$155.30	$155.30
7 purchase totals =	$1,051.00		$1,138.7694	$1,138.77	$1,138.75	$1,138.80