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	$196.56	13.837%	$223.758	$223.76	$223.75	$223.80
Purchase #2	$177.80	4.690%	$186.1388	$186.14	$186.15	$186.10
Purchase #3	$20.69	3.266%	$21.3657	$21.37	$21.35	$21.40
Purchase #4	$43.64	3.816%	$45.3053	$45.31	$45.30	$45.30
Purchase #5	$70.68	5.218%	$74.3681	$74.37	$74.35	$74.40
Purchase #6	$121.55	12.253%	$136.4435	$136.44	$136.45	$136.40
Purchase #7	$99.56	10.266%	$109.7808	$109.78	$109.80	$109.80
7 purchase totals =	$730.48		$797.1602	$797.17	$797.15	$797.20