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	$51.80	4.829%	$54.3014	$54.30	$54.30	$54.30
Purchase #2	$14.37	10.127%	$15.8252	$15.83	$15.85	$15.80
Purchase #3	$74.78	10.641%	$82.7373	$82.74	$82.75	$82.70
Purchase #4	$200.68	13.120%	$227.0092	$227.01	$227.00	$227.00
Purchase #5	$162.46	4.566%	$169.8779	$169.88	$169.90	$169.90
Purchase #6	$73.91	5.562%	$78.0209	$78.02	$78.00	$78.00
Purchase #7	$91.54	7.705%	$98.5932	$98.59	$98.60	$98.60
7 purchase totals =	$669.54		$726.3651	$726.37	$726.40	$726.30