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	$173.78	3.244%	$179.4174	$179.42	$179.40	$179.40
Purchase #2	$222.47	6.869%	$237.7515	$237.75	$237.75	$237.80
Purchase #3	$129.44	8.445%	$140.3712	$140.37	$140.35	$140.40
Purchase #4	$182.44	6.308%	$193.9483	$193.95	$193.95	$193.90
Purchase #5	$59.87	9.123%	$65.3319	$65.33	$65.35	$65.30
Purchase #6	$116.60	11.824%	$130.3868	$130.39	$130.40	$130.40
Purchase #7	$177.78	10.774%	$196.934	$196.93	$196.95	$196.90
7 purchase totals =	$1,062.38		$1,144.1411	$1,144.14	$1,144.15	$1,144.10