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	$220.34	7.867%	$237.6741	$237.67	$237.65	$237.70
Purchase #2	$170.28	8.842%	$185.3362	$185.34	$185.35	$185.30
Purchase #3	$156.90	4.784%	$164.4061	$164.41	$164.40	$164.40
Purchase #4	$79.40	13.398%	$90.038	$90.04	$90.05	$90.00
Purchase #5	$133.33	5.544%	$140.7218	$140.72	$140.70	$140.70
Purchase #6	$228.64	5.870%	$242.0612	$242.06	$242.05	$242.10
Purchase #7	$103.86	5.266%	$109.3293	$109.33	$109.35	$109.30
7 purchase totals =	$1,092.75		$1,169.5667	$1,169.57	$1,169.55	$1,169.50