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	$186.61	5.477%	$196.8306	$196.83	$196.85	$196.80
Purchase #2	$145.77	4.150%	$151.8195	$151.82	$151.80	$151.80
Purchase #3	$80.33	5.528%	$84.7706	$84.77	$84.75	$84.80
Purchase #4	$176.77	4.703%	$185.0835	$185.08	$185.10	$185.10
Purchase #5	$22.96	7.196%	$24.6122	$24.61	$24.60	$24.60
Purchase #6	$94.63	7.397%	$101.6298	$101.63	$101.65	$101.60
Purchase #7	$112.70	13.681%	$128.1185	$128.12	$128.10	$128.10
7 purchase totals =	$819.77		$872.8647	$872.86	$872.85	$872.80