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	$167.60	10.133%	$184.5829	$184.58	$184.60	$184.60
Purchase #2	$37.43	7.676%	$40.3031	$40.30	$40.30	$40.30
Purchase #3	$182.76	10.111%	$201.2389	$201.24	$201.25	$201.20
Purchase #4	$135.31	4.665%	$141.6222	$141.62	$141.60	$141.60
Purchase #5	$245.94	4.626%	$257.3172	$257.32	$257.30	$257.30
Purchase #6	$142.85	7.556%	$153.6437	$153.64	$153.65	$153.60
Purchase #7	$134.44	7.448%	$144.4531	$144.45	$144.45	$144.50
7 purchase totals =	$1,046.33		$1,123.1611	$1,123.15	$1,123.15	$1,123.10