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	9.256%	$196.5625	$196.56	$196.55	$196.60
Purchase #2	$66.31	3.749%	$68.796	$68.80	$68.80	$68.80
Purchase #3	$80.49	7.302%	$86.3674	$86.37	$86.35	$86.40
Purchase #4	$226.61	10.102%	$249.5021	$249.50	$249.50	$249.50
Purchase #5	$110.63	8.841%	$120.4108	$120.41	$120.40	$120.40
Purchase #6	$152.33	13.272%	$172.5472	$172.55	$172.55	$172.50
Purchase #7	$155.64	4.690%	$162.9395	$162.94	$162.95	$162.90
7 purchase totals =	$971.92		$1,057.1255	$1,057.13	$1,057.10	$1,057.10