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	$242.59	6.502%	$258.3632	$258.36	$258.35	$258.40
Purchase #2	$162.96	3.471%	$168.6163	$168.62	$168.60	$168.60
Purchase #3	$204.43	12.217%	$229.4052	$229.41	$229.40	$229.40
Purchase #4	$71.89	13.471%	$81.5743	$81.57	$81.55	$81.60
Purchase #5	$78.31	10.608%	$86.6171	$86.62	$86.60	$86.60
Purchase #6	$217.49	9.265%	$237.6404	$237.64	$237.65	$237.60
Purchase #7	$59.33	3.410%	$61.3532	$61.35	$61.35	$61.40
7 purchase totals =	$1,037.00		$1,123.5697	$1,123.57	$1,123.50	$1,123.60