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	$161.69	3.443%	$167.257	$167.26	$167.25	$167.30
Purchase #2	$182.55	6.529%	$194.4687	$194.47	$194.45	$194.50
Purchase #3	$227.78	5.560%	$240.4446	$240.44	$240.45	$240.40
Purchase #4	$86.43	10.403%	$95.4213	$95.42	$95.40	$95.40
Purchase #5	$45.69	10.607%	$50.5363	$50.54	$50.55	$50.50
Purchase #6	$232.57	9.798%	$255.3572	$255.36	$255.35	$255.40
Purchase #7	$248.91	10.296%	$274.5378	$274.54	$274.55	$274.50
7 purchase totals =	$1,185.62		$1,278.0229	$1,278.03	$1,278.00	$1,278.00