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	$163.32	5.829%	$172.8399	$172.84	$172.85	$172.80
Purchase #2	$115.64	6.536%	$123.1982	$123.20	$123.20	$123.20
Purchase #3	$113.76	5.873%	$120.4411	$120.44	$120.45	$120.40
Purchase #4	$189.46	13.426%	$214.8969	$214.90	$214.90	$214.90
Purchase #5	$25.60	10.244%	$28.2225	$28.22	$28.20	$28.20
Purchase #6	$169.59	7.462%	$182.2448	$182.24	$182.25	$182.20
Purchase #7	$151.64	13.155%	$171.5882	$171.59	$171.60	$171.60
7 purchase totals =	$929.01		$1,013.4316	$1,013.43	$1,013.45	$1,013.30