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	$90.28	5.799%	$95.5153	$95.52	$95.50	$95.50
Purchase #2	$82.67	11.843%	$92.4606	$92.46	$92.45	$92.50
Purchase #3	$152.84	9.823%	$167.8535	$167.85	$167.85	$167.90
Purchase #4	$243.35	10.713%	$269.4201	$269.42	$269.40	$269.40
Purchase #5	$165.72	6.353%	$176.2482	$176.25	$176.25	$176.20
Purchase #6	$20.74	6.538%	$22.096	$22.10	$22.10	$22.10
Purchase #7	$91.56	9.312%	$100.0861	$100.09	$100.10	$100.10
7 purchase totals =	$847.16		$923.6798	$923.69	$923.65	$923.70