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	$109.42	12.470%	$123.0647	$123.06	$123.05	$123.10
Purchase #2	$210.32	5.382%	$221.6394	$221.64	$221.65	$221.60
Purchase #3	$98.86	4.170%	$102.9825	$102.98	$103.00	$103.00
Purchase #4	$25.78	9.628%	$28.2621	$28.26	$28.25	$28.30
Purchase #5	$64.43	4.148%	$67.1026	$67.10	$67.10	$67.10
Purchase #6	$74.32	5.802%	$78.632	$78.63	$78.65	$78.60
Purchase #7	$115.60	6.811%	$123.4735	$123.47	$123.45	$123.50
7 purchase totals =	$698.73		$745.1568	$745.14	$745.15	$745.20