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	$158.73	9.683%	$174.0998	$174.10	$174.10	$174.10
Purchase #2	$70.38	7.789%	$75.8619	$75.86	$75.85	$75.90
Purchase #3	$98.52	12.763%	$111.0941	$111.09	$111.10	$111.10
Purchase #4	$131.88	12.223%	$147.9997	$148.00	$148.00	$148.00
Purchase #5	$93.71	8.711%	$101.8731	$101.87	$101.85	$101.90
Purchase #6	$75.50	3.396%	$78.064	$78.06	$78.05	$78.10
Purchase #7	$137.48	3.331%	$142.0595	$142.06	$142.05	$142.10
7 purchase totals =	$766.20		$831.0521	$831.04	$831.00	$831.20