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	$205.95	8.155%	$222.7452	$222.75	$222.75	$222.70
Purchase #2	$250.92	4.477%	$262.1537	$262.15	$262.15	$262.20
Purchase #3	$50.54	12.545%	$56.8802	$56.88	$56.90	$56.90
Purchase #4	$129.58	9.538%	$141.9393	$141.94	$141.95	$141.90
Purchase #5	$141.42	6.618%	$150.7792	$150.78	$150.80	$150.80
Purchase #6	$80.49	10.222%	$88.7177	$88.72	$88.70	$88.70
Purchase #7	$151.32	10.403%	$167.0618	$167.06	$167.05	$167.10
7 purchase totals =	$1,010.22		$1,090.2771	$1,090.28	$1,090.30	$1,090.30