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	$154.34	13.678%	$175.4506	$175.45	$175.45	$175.50
Purchase #2	$126.25	10.599%	$139.6312	$139.63	$139.65	$139.60
Purchase #3	$162.74	10.306%	$179.512	$179.51	$179.50	$179.50
Purchase #4	$131.68	3.581%	$136.3955	$136.40	$136.40	$136.40
Purchase #5	$206.78	7.692%	$222.6855	$222.69	$222.70	$222.70
Purchase #6	$175.88	6.276%	$186.9182	$186.92	$186.90	$186.90
Purchase #7	$62.63	7.835%	$67.5371	$67.54	$67.55	$67.50
7 purchase totals =	$1,020.30		$1,108.1301	$1,108.14	$1,108.15	$1,108.10