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	$179.91	4.840%	$188.6176	$188.62	$188.60	$188.60
Purchase #2	$113.38	13.689%	$128.9006	$128.90	$128.90	$128.90
Purchase #3	$185.69	11.110%	$206.3202	$206.32	$206.30	$206.30
Purchase #4	$111.50	11.130%	$123.91	$123.91	$123.90	$123.90
Purchase #5	$105.38	3.513%	$109.082	$109.08	$109.10	$109.10
Purchase #6	$171.80	4.485%	$179.5052	$179.51	$179.50	$179.50
Purchase #7	$161.96	12.329%	$181.928	$181.93	$181.95	$181.90
7 purchase totals =	$1,029.62		$1,118.2636	$1,118.27	$1,118.25	$1,118.20