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	$198.43	9.746%	$217.769	$217.77	$217.75	$217.80
Purchase #2	$119.33	4.243%	$124.3932	$124.39	$124.40	$124.40
Purchase #3	$189.98	3.199%	$196.0575	$196.06	$196.05	$196.10
Purchase #4	$199.88	11.196%	$222.2586	$222.26	$222.25	$222.30
Purchase #5	$73.88	6.102%	$78.3882	$78.39	$78.40	$78.40
Purchase #6	$226.32	6.841%	$241.8026	$241.80	$241.80	$241.80
Purchase #7	$100.90	9.564%	$110.5501	$110.55	$110.55	$110.60
7 purchase totals =	$1,108.72		$1,191.2192	$1,191.22	$1,191.20	$1,191.40