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	$149.27	5.336%	$157.235	$157.24	$157.25	$157.20
Purchase #2	$35.70	5.368%	$37.6164	$37.62	$37.60	$37.60
Purchase #3	$118.90	4.150%	$123.8344	$123.83	$123.85	$123.80
Purchase #4	$195.69	10.264%	$215.7756	$215.78	$215.80	$215.80
Purchase #5	$155.90	9.800%	$171.1782	$171.18	$171.20	$171.20
Purchase #6	$72.36	9.813%	$79.4607	$79.46	$79.45	$79.50
Purchase #7	$37.44	13.254%	$42.4023	$42.40	$42.40	$42.40
7 purchase totals =	$765.26		$827.5026	$827.51	$827.55	$827.50