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	$169.34	5.437%	$178.547	$178.55	$178.55	$178.50
Purchase #2	$184.47	9.129%	$201.3103	$201.31	$201.30	$201.30
Purchase #3	$105.64	3.435%	$109.2687	$109.27	$109.25	$109.30
Purchase #4	$82.94	13.243%	$93.9237	$93.92	$93.90	$93.90
Purchase #5	$203.64	4.143%	$212.0768	$212.08	$212.10	$212.10
Purchase #6	$55.48	10.871%	$61.5112	$61.51	$61.50	$61.50
Purchase #7	$198.78	12.340%	$223.3095	$223.31	$223.30	$223.30
7 purchase totals =	$1,000.29		$1,079.9472	$1,079.95	$1,079.90	$1,079.90